Overexpression of DEFECTIVE IN ANTHER DEHISCENCE 1 increases rapeseed silique length through crosstalk between JA and auxin signaling

Abstract

Rapeseed (Brassica napus) is the second largest oilseed crop worldwide. Silique length and seed weight are positively correlated with its yield. Here, a rapeseed gene DEFECTIVE IN ANTHER DEHISCENCE 1 (DAD1; Bna.A05DAD1) was isolated, and its overexpression could significantly increase the SL and SW in Arabidopsis and rapeseed through the enlargement of the silique pericarp cells. Bna.A05DAD1 expression is observed in the seeds and anthers specifically, and its associated protein is localized to the chloroplast. Transcriptomic analysis revealed that the fatty acid biosynthesis and phytohormone response pathways were influenced with Bna.A05DAD1 overexpression. Since the FATTY ACID DESATURASE 2/6 (FAD2/6) and FAD3/7/8 genes were significantly higher than the wild type, the concentrations of linoleic acid and linolenic acid were increased in the DAD1-overexpressing rapeseed plants. Besides, overexpression of Bna.A05DAD1 suppressed the negative regulation of AUXIN RESPONSE FACTOR 18 (ARF18) through upregulation of jasmonate acid (JA) biosynthesis genes (ALLENE OXIDE CYCLASE 4, AOC4; ALLENE OXIDE SYNTHASE, Bna.A02AOS and OXOPHYTODIENOATE-REDUCTASE, Bna.C03OPR), resulting in activating of auxin response genes, leading the auxin to accumulate and the SL and SW increase. Our results suggest new views about the role Bna.A05DAD1 played in regulating fatty acid composition and increasing yield in rapeseed, as well as reveal an important mechanism of the crosstalk between the JA and auxin signaling pathways in the breeding of high-yielding rapeseed.