Integration of genome-wide association studies, metabolomics, and transcriptomics reveals phenolic acid- and flavonoid-associated genes and their regulatory elements under drought stress in rapeseed flowers

Authors: SALAMI, MARYAM - Shiraz University; HEIDARI, BAHRAM - Shiraz University; BATLEY, JACQUELINE - University Of Western Australia; WANG, JIN - Nanjing Agricultural University; TAN, XIAO-LI - Jiangsu University; Richards, Christopher; TAN, HELIN - Jiangsu University

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2023
Publication Date: 1/11/2024
Citation: Salami, M., Heidari, B., Batley, J., Wang, J., Tan, X., Richards, C.M., Tan, H. 2024. Integration of genome-wide association studies, metabolomics, and transcriptomics reveals phenolic acid- and flavonoid-associated genes and their regulatory elements under drought stress in rapeseed flowers. Frontiers in Plant Science. 14. Article e1249142. https://doi.org/10.3389/fpls.2023.1249142.
DOI: https://doi.org/10.3389/fpls.2023.1249142

Interpretive Summary: The main goal of this study was to investigate the genetic regulation of phenolic compounds in rapeseed flowers and understand their role in conferring drought tolerance. Not much is known about how the synthesis of these important bio-active compounds are regulated during growth during stress conditions like drought. This study identified genomic locations within B. napus that influence the expression of polyphenolic compounds during drought stress and provided supporting information for two research areas. One is the development of marker assisted breeding strategies for stress tolerance by disentangling the molecular mechanisms of these traits. The other is to develop genomic resources for developing metabolite associated breeding in the future.

Technical Abstract: Rapeseed (Brassica napus L.) contains wide variety of bioactive components which are beneficial for the human health. Drought stress is a major devastating abiotic factor that influence the quality of rapeseed through phenolic content and antioxidant capacity. To elucidate the genetic basis of phytochemical traits in rapeseed, we performed a genome-wide association analysis of drought-related traits using 52,157 SNPs in 119 rapeseed genotypes under well-watered (WW) and drought stress (DS) conditions. Rapeseed flower was rich in dihydroxybenzoic acids, hydroxycinnamic acids and flavonoids and was acted as an antioxidant agent due to its inhibition of DPPH with 93%, might be attributed to the presence of phenolic compounds including chlorogenic acid and epicatechin. The level of total phenolic compounds and antioxidant activity increased under drought stress and severe enhancement was observed for epicatechin (105.13%) and myricetin (72.26%). A total of 568 SNPs (P < 1.0e-6) were strongly associated with compounds under two conditions, 211 significant associated SNPs under WW condition and 357 significant associated SNPs under DS. We identified 15 and 29 candidate genes under WW and DS conditions, respectively. Transcriptomic analysis identified three candidate genes, as drought-responding genes, including BnaA02g11330D, BnaA02g03720D and BnaA06g05580D were significantly upregulated in rapeseed genotypes with high caffeic and chlorogenic acids under drought stress. Haplotype analysis using significant SNPs revealed various allelic combinations regulating diverse phenotypes for epicatechin, caffeic acid and chlorogenic acid. These results provide clues to understanding the genetic basis of phenolic compounds and changes related to drought tolerance, providing novel loci for generating drought-tolerant rapeseed with high-phenolic compounds.