The amount of free glucose and sucrose within the leaves of Stevia rebaudiana has been evaluated under different photoperiods and related to steviol glycoside (SVgly) accumulation. The diurnal dynamics of glucose and sucrose in leaves, internodes, apices, and roots revealed considerable fluctuations. Within leaves, glucose and sucrose content decreased up to three-fold during the night whereas SVgly amounts did not show any significant diurnal fluctuations. Ontogenetic variations in glucose content was markedly different under long-day (LD) and short-day (SD) regimes. Under LD, glucose content increased two-fold after the onset of flower bud formation, whereas under SD, a stagnation or small decrease was observed. This increase under LD was already noticed in the upper sink leaves at the end of the vegetative stage, possibly acting as a metabolic trigger for the phase transition to reproductive development. Under SD, glucose content appeared more controlled resulting in a better linear relationship with dry matter and SVgly content. The increased sink demands of the transitional apex led to a rapid decline in leaf sucrose which showed little or no correlation with SVgly amounts. From our results, it becomes clear that the correlation between glucose or sucrose as substrates and SVglys as products is very dynamic and is significantly influenced by day-length and ontogeny.

When exposed to an acute ozone stress, cell death occurred in leaves of the O₃ sensitive Populus deltoides × maximowiczii clone Eridano. After treatment (5 h fumigation and 24 h recovery), the damaged areas covered more than 50 % of the leaf surface. At cellular level, these lesions were preceded by some apoptotic hallmarks and by biochemical and physiological alterations evoked by the apoplastic O₃ dissociation. The cell death pattern was highly localized and involved an increase of membrane permeability, externalization of phosphatidylserine, DNA fragmentation, callose accumulation, polyphenol production, and a biphasic oxidative burst accompanied by NO overproduction. These results indicate a process of programmed cell death that could have the biological significance of limiting the spreading the oxidative burst triggered by ozone dissociation in apoplastic environment. Moreover, materials derived from cell dismantling could be remobilized toward developing structures which can conclude their ontogenetic program after the stress.

Lingonberry (Vaccinium vitis-idaea L. ssp. vitis-idaea Britton) cultivars Regal, Splendor, and Erntedank were obtained by conventional softwood cuttings (taken as a control), by in vitro shoot proliferation of node explants, and by adventitious shoot regeneration from excised leaves of micropropagated shoots. In the plants propagated in vitro, the total ascorbate content increased and its pool was more oxidized, the total glutathione content also increased but its pool became more reduced. The leaves of plants obtained from the in vitro culture showed significantly higher antioxidant enzyme activities except for dehydroascorbate reductase which was at a similar level in all plants. Total soluble phenolics, tannins, and flavonoids were enhanced in fruits of in vitro-propagated plants whereas in leaves, the levels of these metabolites (except flavonoids) were higher in ex vitro derived plants. The total radical scavenging capacity was enhanced in berries of the in vitro propagated plants. It is suggested that the active morphogenetic process, characterized by intensive formation and scavenging reactive oxygen species is reflected in the activities of antioxidant enzymes and metabolites. The reduction potential of glutathione is the most important parameter which determines patterns of growth and differentiation in the investigated plants.

Homogeneous low phosphorus availability was reported to regulate root architecture in Arabidopsis via auxin, but the roles of auxin in root architecture plasticity to heterogeneous P availability remain unclear. In this study, we employed auxin biosynthesis-, transport- and signalling-related mutants. Firstly, we found that in contrast to low P (LP) content in the whole medium, primary root (PR) growth of Arabidopsis was partially rescued in the medium divided into two parts: upper with LP and lower with high P (HP) content or in the reverse arrangement. The down part LP was more effective to arrest PR growth as well as to decrease density of lateral roots (DLR) than the upper LP, and effects were dependent on polar auxin transport. Secondly, we verified that auxin receptor TIR1 was involved in the responses of PR growth and lateral root (LR) development to P supply and loss of function of TIR1 inhibited LR development. Thirdly, effects of heterogeneous P on LRD in the upper part of PR was dependent on PIN2 and PIN4, and in the down part on PIN3 and PIN4, whereas density of total LRs was dependent on auxin transporters PIN2 and PIN7. Finally, heterogeneous P availability altered the accumulation of auxin in PR tip and the expression of auxin biosynthesisrelated genes TAA1, YUC1, YUC2, and YUC4. Taken together, we provided evidences for the involvement of auxin in root architecture plasticity in response to heterogeneous phosphorus availability in Arabidopsis.

DNA cassette consisting of an Arabidopsis dehydration-responsive element binding factor 1 (DREB1B) cDNA, driven by a cauliflower mosaic virus 35S promoter, was introduced into potato plants (Solanum tuberosum L.) through Agrobacterium tumefaciens-mediated gene transfer. The presence and expression of the gene in transgenic plants were confirmed by the PCR and RT-PCR techniques, respectively. Northern hybridization using a DREB1B cDNA probe revealed high levels of DREB1B expression among the most transgenic lines. Overexpression of DREB1B imparted a significant freezing and drought tolerance gain in the transgenic potato lines. In comparison with the wild-type plants, the transgenic potatoes contained higher proline content under drought and freezing conditions, and maintained their relative water content higher under water stress. The enhancement of tolerance in transgenic potato highlights the presence of genes responding to the transcription factor DREB1B in this plant.

Alfalfa (Medicago sativa L.) roots were treated with 50 and 100 μg cm^-3 of oligogalacturonide (OGA) solutions with a degree of polymerization between 7 and 15. Changes in the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) as well as ascorbate (ASC) content were determined in crude extract of alfalfa roots after 30, 60 and 120 min of treatment. An increase in the SOD activity was observed in roots treated with 50 and 100 μg cm^-3 OGA, which could be related to its O₂ ^.- scavenging function. As concern H₂O₂ scavenging, CAT activity was increased in the first 30 min by both OGA concentrations, while POX was a key enzyme at higher OGA concentration and treatment duration. ASC content firstly increased upon exposure to high OGA concentration, and then decreased after longer treatment while low OGA concentration had no effect on ASC content.

Changes in membrane lipid composition is a fundamental strategy for plants to resist low-temperature stress. We compared members of 11 membrane glycerolipid classes in Thellungiella salsuginea and its close relative Arabidopsis thaliana at normal growth temperature, and during cold acclimation (CA), freezing (FR), and post-freezing recovery (PFR). The results showed several properties of T. salsuginea distinct from that in A. thaliana, which included: 1) low relative content of phosphatidic acid (PA) and a rapid increase and decrease of PA during FR and PFR respectively; 2) insensitivity of lyso-phospholipids to freezing; and 3) high ratio of phosphatidylcholine to phosphatidylethanolamine. All these properties were in favour of maintaining membrane integrity and stability and therefore enable T. salsuginea to be more tolerant to freezing than A. thaliana.

In transgenic plants, for many applications it is important that the inserted genes are expressed in a tissue-specific manner. This in turn could help better understanding their roles in plant development. Germin-like proteins (GLPs) play diverse roles in plant development and defense responses. In order to understand the functions and regulation of the GLP13 gene, its promoter (762 bp) was cloned and fused with a β-glucuronidase (GUS) reporter gene for transient expression in Arabidopsis thaliana and tobacco (Nicotiana tabacum cv. K326). Histochemical analysis of the transgenic plants showed that GUS was specifically expressed in vascular bundles predominantly in phloem tissue of all organs in Arabidopsis. Further analyses in transgenic tobacco also identified similar GUS expression in the vascular bundles.

The alleviative effects of exogenous calcium on copper phytotoxicity were investigated in Elodea canadensis plants. There was a significant accumulation of Cu in the plants after their exposure to 0.01 mM Cu accompanied by many symptoms of toxicity. Increased uptake of Cu severely reduced content of photosynthetic pigments, soluble proteins, and free proline. The total antioxidant capacity (T-AOC), reduced glutathione (GSH), and non-protein thiol (NP-SH) were severely suppressed in Cu-stressed plants resulting in a rapid increase in content of superoxide anion (O₂ ^.-), hydrogen peroxide, lipid peroxidation, and cell death. Simultaneous application of Ca markedly increased the content of photosynthetic pigments, soluble proteins, free proline, T-AOC, GSH, and NP-SH, and reduced oxidative damage as indicated by lowered content of MDA, O₂ ^.-, and H₂O₂; and decreased cell death. Furthermore, application of Ca reduced Cu uptake and effectively reversed the Cu-induced nutrient imbalance.

Zinc is the most widespread deficient micronutrient in the tea growing soils of India which affects growth of the plants. In order to investigate the structural, physiological, and biochemical changes under Zn stress (i.e. both deficient and excess supply) of tea [Camellia sinensis (L.) O. Kuntze cv. T-78] plants, we treated young plants with ZnSO₄ at 0 (deficiency), 0.3, 3 (optimum), and 30 μM (toxic) concentrations for 8 weeks. Zn deficiency and excess resulted in considerable decrease in shoot and root fresh and dry masses, and transmission electron microscopy (TEM) revealed disorganization of some cellular organelles. Further, Zn-stress decreased net photosynthetic rate (P_N), transpiration rate (E), stomatal conductance (g_s), and content of chlorophylls a and b. On the other hand, content of superoxide anion, malondialdehyde, hydrogen peroxide, and phenols, and electrolyte leakage were elevated in stressed plants. The activities of ascorbate peroxidase, catalase, superoxide dismutase, and peroxidase as well as expression of respective genes were up-regulated under Zn-stress. Nevertheless, antioxidant system as a whole did not afford sufficient protection against oxidative damage.

Plant C2 domain proteins play important roles in diverse cellular processes including growth, development, and membrane targeting, as well as in abiotic and biotic stress adaptations by sensing intracellular Ca²⁺ signals. In this study, we isolated a novel C2 domain protein gene, TaERG3, from wheat infected by Puccinia striiformis f. sp. tritici. TaERG3 was predicted to encode a 144 amino acid protein with molecular mass of 15.68 kD and isoelectric point of 3.93. Analysis of the deduced amino acid sequence of TaERG3 using InterProScan revealed the presence of an N-terminal calciumdependent phospholipid-binding module (C2 domain, 5 to 103). Transient expression analysis showed that the TaERG3 protein was predominately and uniformly localized in the plasmalemma and nucleus of onion epidermal cells. Quantitative real-time PCR analyses indicated that TaERG3 transcript was differentially induced in both incompatible and compatible interactions, as well as by applied abscisic acid (ABA) and CaCl₂. However, the significant transcript changes induced by methyl jasmonate, ethylene, and salicylic acid treatments were not as dramatic as those induced by ABA. TaERG3 was also up-regulated by environmental stimuli including low temperature and high salinity. These results imply that TaERG3 might be involved in wheat defence responses against stripe rust and abiotic stresses in an ABA-dependent signalling pathway.

Phytohormones are indispensable factors regulating plant cell dedifferentiation. In this paper, different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin (KIN) were incorporated in the culture medium and the anatomy of dedifferentiated cells prior to callus formation from Arabidopsis thaliana petiole explants was examined. The results indicated that the cytoplasm of parenchyma cells in the vascular bundle gradually became denser with time of culture only if 2,4-D was included in the medium. The WUSCHEL (WUS) gene was expressed in derivative cells of the vascular bundle after culture for 24 h in the presence of 2,4-D and there was no obvious signal in these cells of cultured petioles with KIN alone. These results suggest that 2,4-D plays an important role in the process of dedifferentiation of vascular bundle cells in Arabidopsis petioles and KIN has no obvious effect on it.

Treatment of potato (Solanum tuberosum) plants with cadmium or abscisic acid (ABA) enhanced the content of StPCS 1 transcript and activity of phytochelatin synthase (PCS) in roots.transcript and activity of phytochelatin synthase (PCS) in roots. These treatments enhanced the contents of ABA and expression of genes coding 9-cis-epoxycarotenoid dioxygenase 1 (NCED1) and basic leucine zipper (b-ZIP).expression of genes coding 9-cis-epoxycarotenoid dioxygenase 1 (NCED1) and basic leucine zipper (b-ZIP). Simultaneous treatment of potato plants with Cd and fluridone (Flu), an inhibitor of ABA biosynthesis, completely halted the Cd-induced transcription of StPCS1, NCED1 and StbZIP genes and limited the increases in PCS activity and ABA content. The data suggest that ABA participates in transduction of the Cd signal to the cells of potato roots.

Information on plant responses to combined ozone and cadmium stresses are scarce and limited to herbaceous species. In this research, two poplar clones (I-214 and Eridano), differently sensitive to O₃, were grown for 5 weeks in pots supplied with 0, 53.5, and 160.5 mg(Cd) kg^-1 (soil d.m.) and then exposed to 15-d O₃ fumigation (0.06 mm³ dm^-3, 5 h a day). The effects of the two stressors, alone or in combination, on Cd, Ca, Fe, and Zn accumulation in above-nad below-ground organs, photosynthesis, leaf pigments, and accumulation of H₂O₂ and NO were investigated. Cadmium induced a reduction in stomatal conductance and a significant accumulation of H₂O₂ and NO in both clones nad negatively affected the carotenoid content in I-214. Ozone, on the other hand, counteracted Cd accumulation in the above-ground organs and significantly increased the xanthophyll de-epoxidation state indicating photoinhibition in O₃-treated plants. Surprisingly, O₃ alone or in combination with Cd decreased H₂O₂ accumulation in I-214. The NO production was generally stimulated by Cd, whereas it decreased following O₃ exposure in I-214. The overall data indicate that Cd and O₃ induced clone specific responses. Moreover, when they were applied in combination, antagonistic rather than synergistic effects were observed.

The pollen tube grows rapidly, exclusively at its tip, to deliver its sperm for fertilization. The polarized tip growth of pollen tubes is dependent on the highly dynamic actin cytoskeleton. Plant LIM proteins (named after initials of containing proteins Lin11, Isl-1, and Mec-3) have been shown to regulate actin bundling in different cells, however, their roles in pollen tube growth have remained obscure. Here, we report the function of Arabidopsis LIM proteins PLIM2a and PLIM2b in pollen tube growth. The PLIM2a mutation resulted in short and swollen Arabidopsis pollen tube with defective actin bundles. The expression of the construct green fluorescent protein (GFP)-PLIM2b led to fluorescence of the actin bundles in germinating pollen and also the long actin bundles along the growing pollen tubes in Arabidopsis, but not of the short and sparse actin bundles that characterize the tip regions of the pollen tubes. There is a partially redundant function between PLIM2a and PLIM2b in the shank actin bundle organization during Arabidopsis pollen tube growth, as PLIM2b could rescue for the defective shank actin bundles in PLIM2a mutation pollen tubes. This report suggests critical roles of PLIM2a/PLIM2b in actin configuration during Arabidopsis pollen germination and tube growth.

Sunflower broomrape (Orobanche cumana Wallr.) is considered a self-fertilizing species, but there is no indication as to whether it is strictly self-fertilized or that it presents some extent of cross-fertilization. The objective of this research was to measure the rate of cross-fertilization in O. cumana using an unpigmented recessive mutant as a visual marker. A pot and a field experiment in which single unpigmented plants were surrounded by a large number of pigmented plants were conducted. Occurrence of F₁ hybrids, readily distinguishable from unpigmented plants in the progenies of unpigmented plants provided a direct measurement of the cross-fertilization rate. Progenies of unpigmented plants contained 21.5 % of F₁ hybrids in the pot experiment and 28.8 % in the field experiment. The results revealed that O. cumana is a partially allogamous species, which has great relevance for understanding the genetic structure and dynamics of populations and, ultimately, race evolution in this parasitic plant.

Annexins play a crucial role in plant development and response to environmental stimuli. In this study, a total of 23 annexin genes (GmANN1 - GmANN23) were identified from the soybean genome database and for two of them (GmANN11 and GmANN14), complete cDNAs were cloned. GmANN1 - GmANN23 encoded a set of predicted proteins which showed high similarity to other known annexins. Most GmANN genes contained four putative annexin repeats. Generally, a type II Ca²⁺-binding site is found to exist in the first and fourth repeats. GmANN1, 10, 11, 12, and 14 showed different organ-specific expression patterns. Furthermore, expression of these five GmANNs was significantly induced by drought and abscisic acid. Expression of four annexins (GmANN1, 11, 12, and 14) was induced by cold and expression of three annexins (GmANN1, 11, and 12) responded to high salinity.

The changes in the activities of antioxidant enzymes and amounts of proteins, phenols, and flavonoids in regenerating and non-regenerating calli during organogenesis of Sterculia urens were monitored. Maximum growth of calli and the most efficient regeneration of shoots occurred on Murashige and Skoog (MS) medium supplemented with 0.5 mg dm^-3 benzylaminopurine (BAP) + 2 or 4 mg dm^-3 naphtalene acetic acid (NAA). Peroxidase (POD), catalase, and superoxide dismutase activities increased in the regenerating calli but decreased in the non-regenerating calli. Six POD isoenzymes were detected. Protein content decreased in the non-regenerating calli and increased significantly during regeneration of shoots from callus. Total phenols and flavonoids increased in the non regenerating calli. SDS-PAGE analysis revealed a role of many proteins in organogenesis.

Paspalum notatum Flügge is a grass species organized as an agamic complex. The objective of the current research was to survey the frequencies and variation of cytosine methylation at CCGG sequences in diploid and tetraploid genotypes, and to determine the occurrence of methylation changes associated with tetraploidization by using methylation-sensitive amplification polymorphism (MSAP) markers. No differences were found in the average proportions of methylated CCGG sites between cytotypes, but methylation patterns were significantly more variable in tetraploids. In both groups of plants, epigenetic and non-epigenetic variation correlated significantly when compared by Mantel tests. The evaluation of 159 common MSAP markers showed that 18.86 % of them differed in their methylation status in the different ploidies. Dendrogram analysis, reflecting epigenetic distances, showed that the four diploids and one experimentally-obtained sexually-reproducing tetraploid, grouped together. MSAP analysis performed on a diploid plant and its autotetraploid derivative showed that new epialleles emerged after tetraploidization. Sequencing of several MASP markers showed homologies with low copy genes, non-coding sequences and transposon/retrotransposon elements.

In the previous research, a novel gene GmPOI (GenBank acc. No. HM235775) encoding a Pollen_Ole_e_I conserved domain was identified in roots of soybean drought resistant cv. Jindou 23. In the present study, GmPOI was cloned and functionally characterized. Real-time quantitative PCR indicated that the expression of GmPOI was induced by drought, cold, salt and abscisic acid in wild-type soybean. The soybean plants overexpressing GmPOI showed higher tolerance to drought stress than wild types. We concluded that GmPOI is probably a novel gene that is involved in the response to various stresses in soybean.

In this work, we report the ectopic expression of the Osmyb4 rice gene, encoding the Myb4 transcription factor, in Nicotiana tabacum and Salvia sclarea. Transcriptional analysis of T₂ homozygous tobacco plants overexpressing Osmyb4 revealed that Myb4 activated the transcription of several genes of the phenylpropanoid pathway such as PAL, C4H, 4CL1, 4CL2 (encoding phenylalanine ammonia-lyase, cinnamic acid 4-hydroxylase, 4-coumarate: Co A ligase1, 4-coumarate: Co A ligase2). Moreover, the Myb4 increased expression of HQT encoding hydroxycinnamoyl-CoA: quinate transferase, which specifically triggers the accumulation of chlorogenic acid (CGA). In addition, increased acccumulation of rosmarinic acid (RA) was found in transgenic plants of both species. These results open the possibility of using the Osmyb4 gene to increase the production of specific bioactive hydroxycinnamates.

To reveal the allelic differentiations at the two genes for fertility restoration (Rf) on chromosomes 1 (Rf3) and 10 (Rf4), 15 chromosome single segment substitution lines (SSSLs) with the Rf3 locus and 18 SSSLs with the Rf4 locus were crossed with Bobai A (BbA), a cytoplasmic male sterility line with wild abortive type of cytoplasm (WA-CMS), respectively. Based on the pollen and seed fertility of the F₁ hybrids, the Rf3 and Rf4 genes were each classified into four alleles, namely Rf3-1, Rf3-2, Rf3-3, and Rf3-4 for Rf3, and Rf4-1, Rf4-2, Rf4-3, and Rf4-4 for Rf4. Out of the 33 SSSLs, an SSSL W23-19-06-06-11 carrying the genotype Rf3-4Rf3-4/Rf4-4Rf4-4 possessed the strongest restoring ability for BbA. To determine the genetic effects of Rf3 and Rf4 for WA-CMS, one BC₃F₂ population possessing the genetic background of W23-19-06-06-11 was generated from the cross between W23-19-06-06-11 and BbA by backcrossing and marker-assisted selection. In the BC₃F₂ population, the plants carrying the Rf3Rf3/Rf4Rf4, Rf3Rf3/rf4rf4, and rf3rf3/Rf4Rf4 genotypes were selected and their phenotyping for pollen and spikelet fertility were evaluated. The result showed that under the genetic background of SSSL W23-19-06-06-11, the effect of Rf4 appeared to be slightly larger than that of Rf3 and their effects were additive for WA-CMS system. These studies will lead to the transfer of Rf genes into adapted cultivars through marker-assisted selection in active hybrid rice breeding programs.

Photosynthetic organisms synthesize the amphipathic antioxidants called tocopherols which are essential components of the human diet. To increase the α-tocopherol (vitamin E) content, Arabidopsis genes encoding homogentisate phytyltransferase (HPT) and tocopherol cyclase (TC) were constitutively expressed individually and in combination (HPT:TC) in tobacco plant by Agrobacterium mediated transformation. The transgene was confirmed by polymerase chain reaction (PCR), transgene expression was studied by reverse transcriptase (RT)-PCR, integration of the transgene in the plant genome was confirmed by Southern blot, and α-tocopherol content was quantified using high performance liquid chromatography (HPLC). The α-tocopherol content in transgenic tobacco plants expressing HPT, TC, and HPT:TC was increased by 5.4-, 4.0-, and 7.1-fold, respectively, when compared to the wild type (WT). These results indicate that, the HPT and TC activities are critical for enhancing the vitamin E content in tobacco plants.

In conifers, relationship between ethylene and the response to inclination are not well understood. The aim of this work was to study the consequence for the application of 2-chloroethyl phosphonic acid (ethephon), compound able to release ethylene, in one-year-old Pinus radiata D. Don seedlings subjected to inclination. In plants exposed to inclination for 15 d, increase in thickness of cell walls, more rounded shape of xylem cells, and accumulation of lignin were observed. Ethephon application accelerated significantly these changes; they can be observed after 5 d of inclination. The quantitative polymerase chain reaction (qPCR) showed up-regulation of transcripts from genes encoding phenylalanine ammonia lyase and cinnamyl alcohol dehydrogenase after inclination and their possible ethylene signal-dependence. As conclusion, morphological changes on stem xylem cells in young seedlings of radiata pine exposed to inclination are similar to those observed in compression wood and they are influenced by ethephon application.

The present study investigates the effects of indole-3-butyric acid (IBA) alone and in combination with myo-inositol on in vitro rooting and biochemical responses in the cherry rootstocks CAB-6P (Prunus cerasus L.) and Gisela 6 (Prunus cerasus × Prunus canescens). For the CAB-6P rootstock, the best results for root number (6.31), fresh mass (FM), dry mass (DM), and rooting percentage (100 %) were obtained on Murashige and Skoog (MS) medium with 2 mg dm^-3 IBA and maximum root length (30.57 mm) was obtained at 1 mg dm^-3 IBA. Myo-inositol suppressed the positive effects of IBA on root length. In the Gisela 6 explants, the inclusion of 2 mg dm^-3 IBA together with 0.5 mg dm^-3 of myo-inositol in the culture medium significantly enhanced root number (9.91) and root FM and DM. The root length was maximum in the combination of the lowest IBA and myo-inositol concentrations (0.5 mg dm^-3). The rooting percentage was the greatest (100 %) with the application of 1 mg dm^-3 IBA alone. In both explants, the application of IBA alone or in combination with myo-inositol resulted in a lower leaf proline content in comparison with the control (without growth regulators). The maximum leaf chlorophyll content was at 1 mg dm^-3 IBA in the CAB-6P whereas at 2 mg dm^-3 IBA and 1 mg dm^-3 myo-inositol in Gisela 6. Addition of myo-inositol mostly increased sugar content in comparison with control or IBA alone in both rootstocks.

We explored the interaction between radiation of different wavelength and jasmonic acid (JA) or brassinosteroids (BR) on leaf senescence-induced oxidative stress. Three approaches were used: 1) jasmonic acid insensitive1-1 (jai1-1) and brassinosteroid-deficient [dumpy (dpy)] mutants were treated with red (R) or far-red (FR) radiation; 2) phytochromedeficient aurea (au) and high pigment-1 (hp-1) (radiation exaggerated response) mutants were treated with methyl jasmonate (MeJA) or epibrassinolide (epiBL); and 3) double mutants au jai1-1 and au dpy were produced. Leaf chlorophyll content, lipid peroxidation, and antioxidant enzyme activities were determined. After senescence induction in detached leaves, we verified that the patterns of chlorophyll degradation of hormonal and photomorphogenic mutants were not significantly different in comparison with original cv. Micro-Tom (MT). Moreover, there was no significant change in lipid peroxidation measured as malondialdehyde (MDA) production, as well as catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) activities in the hormonal mutants. Exogenous BR increased CAT and APX activities in MT, au, and hp-1. As concerns the double mutants, severe reduction in H₂O₂ production which was not accompanied by changes in MDA content, and CAT and APX activities was observed during senescence in au dpy. The results suggest that JA and BR do not participate in light signaling pathway during leaf senescence-induced oxidative stress.

We investigated the role of 24-epibrassinolide (EBR) in the amelioration of phenanthrene (PHE) stress in tomato (Solanum lycopersicum L.). Exposure to PHE (300 μM) significantly decreased shoot and root length (19 and 16 %, respectively), fresh mass (35 and 43 %, respectively), contents of chlorophyll a (26 %), chlorophyll b (27 %) and carotenoids (18 %) in tomato plants. In addition, PHE increased the malondialdehyde (MDA) content (57 %) and activity of secondary metabolism related enzymes glutathione-S-transferase (GST), glucose-6-phosphate dehydrogenase (G6PDH), shikimate dehydrogenase (SKDH), phenylalanine ammonia-lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD). The expression levels of GST1, PPO, SKDH, PAL and CAD genes were also induced by PHE. Importantly, EBR (0.1 μM) alone and in combination with PHE increased the growth, biomass and activity of those enzymes significantly over control and PHE alone, respectively. Consistent with enzymes activities transcript levels of GST1, PPO, SKDH, PAL and CAD were further increased in PHE+EBR over PHE alone. However, MDA content was remarkably decreased in PHE+EBR than PHE alone. Meanwhile, content of phenols, flavonoids and antioxidant activity were increased by PHE and PHE+EBR further increased all those parameters. These observations suggest that EBR regulates secondary metabolism in tomato which might enhance tolerance to PHE.

Actin is the most abundant protein in eukaryotic cells and is a key cytoskeletal component controlling cell morphology and motility. In this study, four MiACT genes were isolated from mango by homological cloning and designated as MiACT1, MiACT4, MiACT7, and MiACT9. Sequence alignments and phylogenetic analysis demonstrated that the four MiACT genes of mango were highly similar to each other at the nucleotide and amino acid levels. All of four MiACT proteins showed high similarity to the known actin proteins from other species. Reverse transcription polymerase chain reaction revealed that the four MiACT genes were constitutively and stably expressed in all organs tested. Application of plant growth regulators and four stress treatments had a remarkable effect on the expression of MiACT4, MiACT7 and MiACT9, whereas expression of MiACT1 was unresponsive. In contrast, the expression profiles of the four MiACT genes were not regulated by diurnal rhythms. Moreover, the expression of MiACT1 was not affected by heavy metal treatments and the transcript level of MiACT1 was rather stable in different days during the post-harvest period either under treatment or not. Our results suggest that the four actin genes play important roles throughout the entire life cycle of mango; the constitutively and stably expressed MiACT1 is the best candidate as an internal standard for differential gene expression analysis in mango.

Two wheat (Triticum aestivum L.) genotypes with varying degree of drought tolerance were used to analyze programmed cell death (PCD) and related biochemical changes under drought stress. Drought induced PCD in leaves, as evident by internucleosomal nDNA fragmentation, was observed in sensitive genotype Nesser. Drought tolerant genotype (FD-83) showed higher peroxidase, superoxide dismutase, and catalase activities and ascorbate content under drought stress compared to sensitive genotype. Total phenolic content increased whereas lipid peroxidation remained un-changed under drought in FD-83. In contrast, drought enhanced the proteases and ascorbate peroxidase activities and lipid peroxidation (MDA content) in Nesser.