Three FT and multiple CEN and BFT genes regulate maturity, flowering, and vegetative phenology in kiwifruit

Abstract

HighlightSequential action of kiwifruit CEN, BFT, and FT genes regulates growth, dormancy, and flowering. Two differentially expressed FT genes have different impacts on flowering and plant morphology.

Mutagenesis of kiwifruit CENTRORADIALIS‐like genes transforms a climbing woody perennial with long juvenility and axillary flowering into a compact plant with rapid terminal flowering

“…These phenotypes, particularly the altered architecture with increased lateral branching and insensitivity to environmental conditions initiating bud‐set and dormancy, were in common with trees overexpressing FT genes (Endo et al ., ; Klocko et al ., ; Srinivasan et al ., ), demonstrating common outcomes of altered FT/CEN balances. While ectopic overexpression of kiwifruit FT genes gave rise to in vitro flowers (Moss et al ., ; Voogd et al ., ), the terminating effect of mutations in AcCEN4 and AcCEN became evident in the stage when the flowering activator AcFT expression was detectable, suggesting that the mutations affecting CEN genes are only relevant in the presence of a functional FT, as previously emphasized in tomato (Lifschitz et al ., ).…”

“…Previously, five kiwifruit CEN ‐like genes have been identified (Voogd et al ., ). This gene duplication and divergence would be expected to contribute to the regulation of kiwifruit architecture and flowering, but it has been highly problematic to differentiate their endogenous roles, functionally distinguish paralogous genes and generate mutations specifically affecting one or more alleles and members of this gene family.…”

“…Kiwifruit has multiple CEN-like genes which can act as conserved floral repressors (Voogd et al, 2017). Relatively high expression of AcCEN4 and AcCEN in actively growing shoot tips and in latent axillary buds, respectively (Figure 1a), identified these two kiwifruit CEN-like genes as prime candidates for regulation of kiwifruit architecture, maturity and flowering time.…”

“…The RNAseq experiment was described before (Voogd et al, 2017). Briefly, A. chinensis axillary and terminal buds were collected at regular intervals over the season, subjected to RNAseq, and uniquely mapped reads with no mismatches per paired alignment were used to determine gene expression.…”

“…Studies in diploid kiwifruit A. chinensis revealed three FT genes and five CEN-like genes, with overexpression of FT genes resulting in extreme precocity, repression of vegetative growth and development of poorly differentiated in vitro flowers; in contrast, overexpression of all Actinidia CEN-like genes delayed flowering in Arabidopsis and overexpression of AcCEN fully repressed flowering in Actinidia eriantha (Moss et al, 2018;Varkonyi-Gasic et al, 2013;Voogd et al, 2017). We hypothesized that the multiple CEN homologs evolved to control the balance of vegetative growth and flowering in kiwifruit, to regulate the first onset of flowering, and terminal and axillary meristem identity.…”