Xin Youchao, Meng Shuai, Ma Bi, He Wenmin, He Ningjia
State Key Laboratory of Silkworm Genome Biology, Southwest University, Beibei, Chongqing, 400715, China.
State Key Laboratory of Silkworm Genome Biology, Southwest University, Beibei, Chongqing, 400715, China.
Plant Sci. 2020 Jul;296:110473. doi: 10.1016/j.plantsci.2020.110473. Epub 2020 Mar 19.
Proanthocyanidins (PAs) are major defense-related phenolics in mulberry, but the mechanism underlying their biosynthesis remains uncharacterized. In this study, the relationship between the expression of genes encoding anthocyanidin reductase (ANR) or leucoanthocyanidin reductase (LAR) and PA biosynthesis was investigated in white and red mulberry fruits. In ripening fruits, the MnANR and MnLAR transcription levels tended to decrease, whereas the catechin and epicatechin contents initially increased and then decreased. In contrast, the PA content exhibited a clearly different trend. The ectopic expression of MnANR and MnLAR in tobacco increased the resistance to Botrytis cinerea, as evidenced by the less extensive disease symptoms of the transgenic plants compared with the wild-type plants. In vitro experiments revealed that the transgenic tobacco crude leaf extract had an obvious inhibitory effect on B. cinerea. Moreover, the ectopic expression of MnANR and MnLAR in tobacco inhibited the expression of anthocyanin biosynthesis genes, resulting in decreased anthocyanin contents in flowers. The results of this study may be useful for elucidating the mechanism underlying PA biosynthesis. Furthermore, ANR and LAR represent potential targets for improving the resistance of mulberry and related plant species to B. cinerea.
原花青素(PAs)是桑树中与防御相关的主要酚类物质,但其生物合成的潜在机制仍不清楚。在本研究中,对白色和红色桑椹果实中编码花青素还原酶(ANR)或无色花青素还原酶(LAR)的基因表达与PA生物合成之间的关系进行了研究。在成熟果实中,MnANR和MnLAR的转录水平趋于下降,而儿茶素和表儿茶素含量最初增加,然后下降。相比之下,PA含量呈现出明显不同的趋势。MnANR和MnLAR在烟草中的异位表达增强了对灰霉病菌的抗性,与野生型植株相比,转基因植株的病害症状较轻即证明了这一点。体外实验表明,转基因烟草粗叶提取物对灰霉病菌有明显的抑制作用。此外,MnANR和MnLAR在烟草中的异位表达抑制了花青素生物合成基因的表达,导致花朵中的花青素含量降低。本研究结果可能有助于阐明PA生物合成的潜在机制。此外,ANR和LAR是提高桑树及相关植物物种对灰霉病菌抗性的潜在靶点。