Abstract
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.
Highlights
IntroductionThere are approximately 375,000 species of vascular plants globally that generate over 90%
There are approximately 375,000 species of vascular plants globally that generate over 90%of terrestrial productivity [1]
The thickness of the xylem layer decreased by 28% (Figure 3a,f,k), the numbers of sclerenchymatous cell and vessel in the whole cross section of stem decreased by 28% and 59%, and the numbers of sclerenchymatous cell and vessel in a single vascular bundle of stem decreased by 24% and 56%, respectively, in the transgenic plants (Figure 3b–e,g–j; Table 1)
Summary
There are approximately 375,000 species of vascular plants globally that generate over 90%. After overexpressing PtrMYB152 in poplar or A. thaliana, PtrMYB152 increased xylem thickness, secondary cell wall thickness, the content of lignin and expression of the genes related to lignin biosynthesis pathway in the stem of transgenic plants The plant morphology, yield potential, vascular lignification, xylem thickness and cell numbers were drastically inhibited, the lodging resistance was considerably weakened, but the resistance to S. sclerotiorum was greatly enhanced accompanied with great increase in pectin content, after suppression of the BnMYB43 gene family in oilseed rape. These results are beneficial to contemporary oilseed rape breeding or others crops As of it is not well clear about the regulatory mechanisms among vascular bundle formation, biochemical composition changes of secondary xylem, plant morphogenesis and plant disease resistance, or the occurrence and transmission of defense signals in plant growth and development. The research based on the special regulatory node of BnMYB43 is very necessary
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