Genome-Wide Association Study Identifies Candidate Genes Related to the Linoleic Acid Content in Soybean Seeds

Abstract

Soybean (<i>Glycine max</i> (L.) Merrill) oil is a complex mixture of five fatty acids (palmitic, stearic, oleic, linoleic, and linolenic). The high content of linoleic acid (LA) contributes to the oil having poor oxidative stability. Therefore, soybean seed with a lower LA content is desirable. To investigate the genetic architecture of LA, we performed a genome-wide association study (GWAS) using 510 soybean cultivars collected from China. The phenotypic identification results showed that the content of LA varied from 36.22% to 72.18%. The GWAS analysis showed that there were 37 genes related to oleic acid content, with a contribution rate of 7%. The candidate gene <i>Glyma.04G116500.1</i> (<i>GmWRI14</i>) on chromosome 4 was detected in three consecutive years. The <i>GmWRI14</i> showed a negative correlation with the LA content and the correlation coefficient was -0.912. To test whether <i>GmWRI14</i> can lead to a lower LA content in soybean, we introduced <i>GmWRI14</i> into the soybean genome. Matrix-assisted laser desorption/ionization time-of-flight imaging mass spectrometry (MALDI-TOF IMS) showed that the overexpression of <i>GmWRI14</i> leads to a lower LA content in soybean seeds. Meanwhile, RNA-seq verified that <i>GmWRI14</i>-overexpressed soybean lines showed a lower accumulation of <i>GmFAD2-1A</i> and <i>GmFAD2-1B</i> than control lines. Our results indicate that the down-regulation of the <i>FAD2</i> gene triggered by the transcription factor <i>GmWRI14</i> is the underlying mechanism reducing the LA level of seed. Our results provide novel insights into the genetic architecture of LA and pinpoint potential candidate genes for further in-depth studies.