Arabidopsis thaliana MYB43 (AtMYB43) is suggested to be involved in cell wall lignification. PtrMYB152, the Populus orthologue of AtMYB43, is a transcriptional activator of lignin biosynthesis and vessel wall deposition. In this research, MYB43 genes from Brassica napus (rapeseed) and its parental species B. rapa and B. oleracea were molecularly characterized, which were dominantly expressed in stem and other vascular organs and showed responsiveness to Sclerotinia sclerotiorum infection. The BnMYB43 family was silenced by RNAi, and the transgenic rapeseed lines showed retardation in growth and development with smaller organs, reduced lodging resistance, fewer silique number and lower yield potential. The thickness of the xylem layer decreased by 28%; the numbers of sclerenchymatous cells, vessels, interfascicular fibers, sieve tubes and pith cells in the whole cross section of the stem decreased by 28%, 59%, 48%, 34% and 21% in these lines, respectively. The contents of cellulose and lignin decreased by 17.49% and 16.21% respectively, while the pectin content increased by 71.92% in stems of RNAi lines. When inoculated with S. sclerotiorum, the lesion length was drastically decreased by 52.10% in the stems of transgenic plants compared with WT, implying great increase in disease resistance. Correspondingly, changes in the gene expression patterns of lignin biosynthesis, cellulose biosynthesis, pectin biosynthesis, cell cycle, SA- and JA-signals, and defensive pathways were in accordance with above phenotypic modifications. These results show that BnMYB43, being a growth-defense trade-off participant, positively regulates vascular lignification, plant morphology and yield potential, but negatively affects resistance to S. sclerotiorum. Moreover, this lignification activator influences cell biogenesis of both lignified and non-lignified tissues of the whole vascular organ.

中文翻译：

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油菜（欧洲油菜）中的 MYB43 积极调节血管木质化、植物形态和产量潜力，但消极影响对核盘菌的抗性

拟南芥 MYB43 (AtMYB43) 被认为参与细胞壁木质化。PtrMYB152 是 AtMYB43 的杨树直系同源物，是木质素生物合成和血管壁沉积的转录激活剂。在这项研究中，来自欧洲油菜（油菜）及其亲本 B. rapa 和 B. oleracea 的 MYB43 基因被分子表征，它们在茎和其他维管器官中显性表达，并显示出对核盘菌感染的反应性。BnMYB43 家族被 RNAi 沉默，转基因油菜籽品系生长发育迟缓，器官变小，抗倒伏性降低，长角果数量减少，产量潜力降低。木质部厚度减少28%；厚壁细胞、血管、束间纤维的数量，在这些品系中，茎的整个横截面中的筛管和髓细胞分别减少了 28%、59%、48%、34% 和 21%。RNAi株系茎中纤维素和木质素含量分别降低17.49%和16.21%，果胶含量增加71.92%。接种 S. sclerotiorum 后，与 WT 相比，转基因植物茎中的病斑长度显着减少了 52.10%，意味着抗病性大大提高。相应地，木质素生物合成、纤维素生物合成、果胶生物合成、细胞周期、SA 和 JA 信号以及防御途径的基因表达模式的变化与上述表型修饰一致。这些结果表明 BnMYB43 作为生长防御权衡参与者，积极调节血管木质化，植物形态和产量潜力，但对 S. sclerotiorum 的抗性有负面影响。此外，这种木质化激活剂影响整个血管器官的木质化和非木质化组织的细胞生物发生。