Axillary buds are dwarfed shoots that tightly regulate GA pathway and GA-inducible 1,3-beta-glucanase genes during branching in hybrid aspen

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Rinne , P L H , Paul , L K , Vahala , J , Kangasjärvi , J & van der Schoot , C 2016 , ' Axillary buds are dwarfed shoots that tightly regulate GA pathway and GA-inducible 1,3-beta-glucanase genes during branching in hybrid aspen ' , Journal of Experimental Botany , vol. 67 , no. 21 , pp. 5975-5991 . https://doi.org/10.1093/jxb/erw352

Title: Axillary buds are dwarfed shoots that tightly regulate GA pathway and GA-inducible 1,3-beta-glucanase genes during branching in hybrid aspen
Author: Rinne, Päivi L. H.; Paul, Laju K.; Vahala, Jorma; Kangasjärvi, Jaakko; van der Schoot, Christiaan
Contributor: University of Helsinki, Biosciences
University of Helsinki, Biosciences
Date: 2016-11
Language: eng
Number of pages: 17
Belongs to series: Journal of Experimental Botany
ISSN: 0022-0957
URI: http://hdl.handle.net/10138/225035
Abstract: Axillary buds uniquely regulate gibberellin (GA) pathway genes, enabling them to stay inhibited but simultaneously poised for growth. Decapitation promotes expression of GA-inducible 1,3-beta-glucanase genes that function to reinvigorate symplasmic connections to the stem.Axillary buds (AXBs) of hybrid aspen (Populus tremulaxP. tremuloides) contain a developing dwarfed shoot that becomes para-dormant at the bud maturation point. Para-dormant AXBs can grow out after stem decapitation, while dormant AXBs pre-require long-term chilling to release them from dormancy. The latter is mediated by gibberellin (GA)-regulated 1,3-beta-glucanases, but it is unknown if GA is also important in the development, activation, and outgrowth of para-dormant AXBs. The present data show that para-dormant AXBs up-regulate GA receptor genes during their maturation, but curtail GA biosynthesis by down-regulating the rate-limiting GIBBERELLIN 3-OXIDASE2 (GA3ox2), which is characteristically expressed in the growing apex. However, decapitation significantly up-regulated GA3ox2 and GA(4)-responsive 1,3-beta-glucanases (GH17-family; alpha-clade). In contrast, decapitation down-regulated gamma-clade 1,3-beta-glucanases, which were strongly up-regulated in maturing AXBs concomitant with lipid body accumulation. Overexpression of selected GH17 members in hybrid aspen resulted in characteristic branching patterns. The alpha-clade member induced an acropetal branching pattern, whereas the gamma-clade member activated AXBs in recurrent flushes during transient cessation of apex proliferation. The results support a model in which curtailing the final step in GA biosynthesis dwarfs the embryonic shoot, while high levels of GA precursors and GA receptors keep AXBs poised for growth. GA signaling, induced by decapitation, reinvigorates symplasmic supply routes through GA-inducible 1,3-beta-glucanases that hydrolyze callose at sieve plates and plasmodesmata.
Subject: Apical dominance
axillary branching
bud dormancy
callose
gibberellin
1,3-beta-glucanase
para-dormancy
plasmodesmata
Populus
strigolactone
FLOWERING-LOCUS-T
APICAL DOMINANCE
ARABIDOPSIS-THALIANA
GIBBERELLIN BIOSYNTHESIS
PHENOTYPIC PLASTICITY
FREEZING TOLERANCE
TREE ARCHITECTURE
SELF-ORGANIZATION
DORMANCY CALLOSE
AUXIN
1183 Plant biology, microbiology, virology
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