Overexpression of dihydroflavonol 4-reductase (CoDFR) boosts flavonoid production involved in the anthracnose resistance

Abstract

The outbreak of anthracnose caused by <i>Colletotrichum</i> spp. represents a devastating epidemic that severely affects oil tea (<i>Camellia oleifera</i>) production in China. However, the unknown resistance mechanism to anthracnose in <i>C. oleifera</i> has impeded the progress of breeding disease-resistant varieties. In this study, we investigated the physiological responses of resistant and susceptible lines during <i>C. gloeosporioides</i> infection. Our results showed that the accumulation of malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) in both disease-resistant and susceptible lines increased by <i>C. gloeosporioides</i> infection. Also, disease-resistant lines exhibited lower MDA, but higher POD, SOD, and CAT activities compared to susceptible lines. The accumulation of flavonoids in both resistant and susceptible <i>C. oleifera</i> leaves increased following <i>C. gloeosporioides</i> infection, and the increase was greater in resistant lines. Further, we identified and functionally characterized the dihydroflavonol 4-reductase (<i>CoDFR</i>) from the resistant <i>C. oleifera</i> line. We showed that the full-length coding sequence (CDS) of <i>CoDFR</i> is 1044 bp encoding 347 amino acids. The overexpression of <i>CoDFR</i> in tobacco altered the expression of flavonoid biosynthetic genes, resulting in an increased flavonoid content in leaves. <i>CoDFR</i> transgenic tobacco plants exhibited increased anthracnose resistance. Furthermore, the transgenic plants had higher salicylic acid content. These findings offer potential insights into the pivotal role of <i>CoDFR</i> involved in flavonoid-mediated defense mechanisms during anthracnose invasion in resistant <i>C. oleifera</i>.