Camellia oleifera (Ca. oleifera) is a woody tree species cultivated for the production of edible oil from its seed. The growth and yield of tea-oil trees are severely affected by anthracnose (caused by Colletotrichum gloeosporioides). In this study, the transcriptomic and metabolomic analyses were performed to detect the key transcripts and metabolites associated with differences in the susceptibility between anthracnose-resistant (ChangLin150) and susceptible (ChangLin102) varieties of Ca. oleifera. In total, 5001 differentially expressed genes (DEGs) were obtained, of which 479 DEGs were common between the susceptible and resistant varieties and further analyzed. KEGG enrichment analysis showed that these DEGs were significantly enriched in tyrosine metabolism, phenylpropanoid biosynthesis, flavonoid biosynthesis and isoquinoline alkaloid biosynthesis pathways. Furthermore, 68 differentially accumulated metabolites (DAMs) were detected, including flavonoids, such as epicatechin, phenethyl caffeate and procyanidin B2. Comparison of the DEGs and DAMs revealed that epicatechin, procyanidin B2 and arachidonic acid (peroxide free) are potentially important. The expression patterns of genes involved in flavonoid biosynthesis were confirmed by qRT-PCR. These results suggested that flavonoid biosynthesis might play an important role in the fight against anthracnose. This study provides valuable molecular information about the response of Ca. oleifera to Co. gloeosporioides infection and will aid the selection of resistant varieties using marker-assisted breeding.

The outbreak of anthracnose caused by Colletotrichum spp. represents a devastating epidemic that severely affects oil tea (Camellia oleifera) production in China. However, the unknown resistance mechanism to anthracnose in C. oleifera has impeded the progress of breeding disease-resistant varieties. In this study, we investigated the physiological responses of resistant and susceptible lines during C. gloeosporioides 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 C. gloeosporioides 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 C. oleifera leaves increased following C. gloeosporioides infection, and the increase was greater in resistant lines. Further, we identified and functionally characterized the dihydroflavonol 4-reductase (CoDFR) from the resistant C. oleifera line. We showed that the full-length coding sequence (CDS) of CoDFR is 1044 bp encoding 347 amino acids. The overexpression of CoDFR in tobacco altered the expression of flavonoid biosynthetic genes, resulting in an increased flavonoid content in leaves. CoDFR 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 CoDFR involved in flavonoid-mediated defense mechanisms during anthracnose invasion in resistant C. oleifera.

No abstract