An APETALA1 ortholog affects plant architecture and seed yield component in oilseed rape (Brassica napus L.)

Increasing the productivity of rapeseed as one of the widely cultivated oil crops in the world is of upmost importance. As flowering time and plant architecture play a key role in the regulation of rapeseed yield, understanding the genetic mechanism underlying these traits can boost the rapeseed breeding. Meristem identity genes are known to have pleiotropic effects on plant architecture and seed yield in various crops. To understand the function of one of the meristem identity genes, APETALA1 (AP1) in rapeseed, we performed phenotypic analysis of TILLING mutants under greenhouse conditions. Three stop codon mutant families carrying a mutation in Bna.AP1.A02 paralog were analyzed for different plant architecture and seed yield-related traits.

It was evident that stop codon mutation in the K domain of Bna.AP1.A02 paralog caused significant changes in flower morphology as well as plant architecture related traits like plant height, branch height, and branch number. Furthermore, yield-related traits like seed yield per plant and number of seeds per plants were also significantly altered in the same mutant family. Apart from phenotypic changes, stop codon mutation in K domain of Bna.AP1.A02 paralog also altered the expression of putative downstream target genes like Bna.TFL1 and Bna.FUL in shoot apical meristem (SAM) of rapeseed. Mutant plants carrying stop codon mutations in the COOH domain of Bna.AP1.A02 paralog did not have a significant effect on plant architecture, yield-related traits or the expression of the downstream targets.

We found that Bna.AP1.A02 paralog has pleiotropic effect on plant architecture and yield-related traits in rapeseed. The allele we found in the current study with a beneficial effect on seed yield can be incorporated into rapeseed breeding pool to develop new varieties.