biologia plantarum

Biologia plantarum 62:762-774, 2018 | DOI: 10.1007/s10535-018-0819-y

In vitro regeneration for two Populus hybrid clones. The role of pectin domains in cell processes underlying shoot organogenesis induction

P. García-Angulo¹, I. Villar², L. Giner-Robles³, M. L. Centeno^1,*

¹ Plant Physiology Laboratory, Department of Plant Engineering and Sciences, University of León, León, Spain

² Experimental Centre of Aula Dei (CSIC), Zaragoza, Spain

³ Biomedical and Biotechnological Institute of Cantabria Albert Einstein, Santander, Spain

An efficient plant regeneration protocol has been established for two commercial Populus hybrid clones, MC (Populus × euramericana) and UNAL (Populus × interamericana). The culture of internode segments on Murashige and Skoog (MS) medium with 0.5 μM α-naphthalene acetic acid (NAA) and 4 μM N⁶-benzyladenine for 7 weeks (2 weeks in absence of activated charcoal and 5 weeks in its presence) resulted in the highest frequency of shoot regeneration (100 % for MC and 82 % for UNAL). All regenerated shoots longer than 2 cm rooted on half-strength MS medium, independent of the addition of 0.1 μM NAA. Nevertheless, shoots developed better-formed roots in NAA-free medium, which had a positive effect on the acclimatization of plants. In order to know the cellular processes underlying in vitro shoot organogenesis, a histological study was made in UNAL internode-explants. Results revealed that in vitro culture caused swelling around the cut-off zones in all explants, but only those undergoing organogenesis formed proliferation centers under subepidermal cells, which led to formation of bud primordia. Moreover, in vivo tissues and explants with different in vitro response showed different immunolabelling patterns when they were treated with fluorescentmonoclonal antibodies directed to several pectin-polysaccharides of the cell wall. Results allow us to assign a predominant role of homogalacturonan with a low degree of methyl-esterification in the initiation of bud primordia, role of β-1,4-D-galactan side chains of rhamnogalacturonan-I in the cellular differentiation, role of α-1,5-L-arabinan side chains of rhamnogalacturonan-I and of homogalacturonan with a high degree of methyl-esterification in cell division and growth.

Keywords: cell wall; homogalacturonan; immunohistochemistry; micropropagation; poplar; rhamnogalacturonan-I

Subjects: in vitro culture; shoot regeneration; immunohistochemical localization; pectins; callus induction; phytohormones; poplar

Received: January 30, 2018; Revised: May 11, 2018; Accepted: May 21, 2018; Published: August 1, 2018  Show citation