title: The regulatory gamma subunit SNF4b of the sucrose non-fermenting-related kinase complex is involved in longevity and stachyose accumulation during maturation of Medicago truncatula seeds.
abstract: The sucrose non-fermenting-related kinase complex (SnRK1) is a heterotrimeric complex that plays a central role in metabolic adaptation to nutritional or environmental stresses. Here we investigate the role of a regulatory gamma-subunit of the complex, MtSNF4b, in Medicago truncatula seeds. Western blot indicated that MtSNF4b accumulated during seed filling, whereas it disappeared during imbibition of mature seeds. Gel filtration chromatography suggested that MtSNF4b assembled into a complex (450-600 kDa) at the onset of maturation drying, and dissociated during subsequent imbibition. Drying of desiccation-tolerant radicles led to a reassembly of the complex, in contrast to sensitive tissues. Silencing of MtSNF4b using a RNA interference (RNAi) approach resulted in a phenotype with reduced seed longevity, evident from the reduction in both germination percentage and seedling vigour in aged RNAi MtSNF4b seeds compared with the wild-type seeds. In parallel to the assembly of the complex, seeds of the RNAi MtSNF4b lines showed impaired accumulation of raffinose family oligosaccharides compared with control seeds. In mature seeds, the amount of stachyose was reduced by 50-80%, whereas the sucrose content was 60% higher. During imbibition, the differences in non-reducing sugar compared with the control disappeared in parallel to the disassembly of the complex. No difference was observed in dry weight or reserve accumulation such as proteins, lipids and starch. These data suggest that the regulatory gamma-subunit MtSNF4b confers a specific and temporal function to SnRK1 complexes in seeds, improving seed longevity and affecting the non-reducing sugar content at later stages of seed maturation.
authors.affiliation: Unité Mixte de Recherche 1191 Physiologie Moléculaire des Semences (Université d'Angers, Institut National d'Horticulture, Institut National de la Recherche Agronomique), 16 boulevard Lavoisier, 49045 Angers, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Rosnoblet
authors.forename: Catherine
authors.initials: C
authors.lastname: Aubry
authors.forename: Olivier
authors.initials: O
authors.lastname: Leprince
authors.forename: Benoit Ly
authors.initials: BL
authors.lastname: Vu
authors.forename: Hélène
authors.initials: H
authors.lastname: Rogniaux
authors.forename: Julia
authors.initials: J
authors.lastname: Buitink
mesh_terms: D018525:Germination / Q000502:physiology; D008136:Longevity / Q000502:physiology; D046913:Medicago truncatula / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D046912:Multiprotein Complexes / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D034622:RNA Interference; D012639:Seeds / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D013395:Sucrose / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D046912:Multiprotein Complexes; D009844:Oligosaccharides; D010940:Plant Proteins; D014867:Water; C005695:stachyose; D013395:Sucrose; C071570:SNF1-related protein kinases; D017346:Protein Serine-Threonine Kinases