The Arabidopsis geneRGOmediates cytokinin responses and increases seed yield

Abstract

17One-sentence summary: RGO, a novel gene from Arabidopsis, is essential for plant development, 18 mediates CK signaling and increases seed yield in Arabidopsis and rapeseed when overexpressed. Abstract 1 A novel gene, At1g77960, from Arabidopsis thaliana was characterized. At1g77960 transcripts 2 accumulate to very high levels in plants ectopically overexpressing the Golden2-like1 (GLK1) 3 transcription factor and is designated as a Response to GLK1 Overexpression (RGO) gene. RGO 4 encodes a protein with domains of tandem QH and QN repeats. Transcripts and promoter GUS 5 reporter analyses indicated that RGO is expressed in roots, leaves, stems, floral and siliques tissues 6 but not in seeds. Expression of the RGO:YFP fusion protein demonstrated that RGO is localized 7 to the endoplasmic reticulum. MicroRNA mediated silencing of RGO resulted in severe reductions 8 in vegetative and root growth, delayed flowering and reduced seed yield and viability, suggesting 9 that RGO is essential for plant development. Conversely, ectopic overexpression of RGO resulted 10 in enhanced vegetative growth including increased axillary bud formation and a 20% higher seed 11 yield. Stable overexpression of RGO in Brassica napus also produced a similar increase in seed 12 yield. Cytokinin (CK) response assays including root growth, green calli formation from excised 13 hypocotyls and chlorophyll retention during dark-induced senescence suggest that one role of RGO 14 is to mediate CK responses in plant development. These results suggest that RGO could be a target 15 gene for increasing crop seed yields. 16 Keywords 17 Arabidopsis thaliana, At1g77960, GLK1 overexpression, cytokinin response, seed yield 18 19 [Type text] [Type text] 4 1A direct link between GLKs and CK signalling however, is lacking. There is evidence to suggest 2 that type B ARRs coordinate the expression of HY5 (elongated hypocotyl 5), which is required by 3 GLK2 for maximal (although not essential) greening in roots (Kobayashi et al., 2012).