Mewalal Ritesh, Mizrachi Eshchar, Coetzee Berdine, Mansfield Shawn D, Myburg Alexander A
Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private bag X20, Pretoria, 0028, South Africa.
Department of Chemical Engineering, University of Pretoria, Private bag X20, Pretoria, 0028, South Africa.
PLoS One. 2016 Mar 1;11(3):e0150254. doi: 10.1371/journal.pone.0150254. eCollection 2016.
DUF1218 is a land plant-specific innovation and has previously been shown to be associated with cell wall biology, vasculature patterning and abiotic/biotic stress response. The Arabidopsis genome encodes 15 members, two of which (At1g31720 and At4g27435) are preferentially expressed in the secondary cell wall depositing inflorescence stems. To further our understanding of the roles of DUF1218-containing proteins in secondary cell wall biology, we functionally characterized At1g31720 (herein referred to as MODIFYING WALL LIGNIN-1 or MWL-1). Since related gene family members may contribute to functional redundancy, we also characterized At4g19370 (MWL-2), the most closely related gene to MWL-1 in the protein family. Subcellular localization revealed that both Arabidopsis proteins are targeted to the cell periphery. The single T-DNA knockout lines, mwl-1 and mwl-2, and independent overexpression lines showed no significant differences in plant growth or changes in total lignin content relative to wild-type (WT) control plants. However, the double homozygous mutant, mwl-1/mwl-2, had smaller rosettes with a significant decrease in rosette fresh weight and stem height relative to the WT control at four weeks and six weeks, respectively. Moreover, mwl-1/mwl-2 showed a significant reduction in total lignin content (by ca. 11% relative to WT) and an increase in syringyl/guaiacyl (S/G) monomer ratio relative to the control plants. Our study has identified two additional members of the DUF1218 family in Arabidopsis as novel contributors to secondary cell wall biology, specifically lignin biosynthesis, and these proteins appear to function redundantly.
DUF1218是陆地植物特有的创新结构，此前已证明它与细胞壁生物学、维管系统模式形成以及非生物/生物胁迫反应有关。拟南芥基因组编码15个成员，其中两个（At1g31720和At4g27435）在次生细胞壁沉积的花序茎中优先表达。为了进一步了解含DUF1218蛋白在次生细胞壁生物学中的作用，我们对At1g31720（在此称为修饰壁木质素-1或MWL-1）进行了功能表征。由于相关基因家族成员可能导致功能冗余，我们还对At4g19370（MWL-2）进行了表征，它是该蛋白家族中与MWL-1关系最密切的基因。亚细胞定位显示，这两种拟南芥蛋白都定位于细胞周边。与野生型（WT）对照植物相比，单T-DNA敲除系mwl-1和mwl-2以及独立的过表达系在植物生长或总木质素含量变化方面没有显著差异。然而，双纯合突变体mwl-1/mwl-2的莲座叶较小，在四周和六周时，相对于WT对照，莲座叶鲜重和茎高分别显著降低。此外（Moreover），mwl-1/mwl-2的总木质素含量显著降低（相对于WT约降低11%），并且相对于对照植物，紫丁香基/愈创木基（S/G）单体比率增加。我们的研究在拟南芥中鉴定出DUF1218家族的另外两个成员，它们是次生细胞壁生物学（特别是木质素生物合成）的新贡献者，并且这些蛋白似乎具有冗余功能。
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