拟南芥MAG2和同源蛋白MAL缺失对生长素极性运输的影响

Vesicle transport is the basic of various life activities of cells. In our previous work, we found that Arabidopsis MAG2, MIP1,2 and MIP3 form a tethering complex, regulating fusion of transport vesicle to the ER membrane during ER-Golgi retrograde transport. When these genes are defective, exit from the ER of proteins is blocked, resulting in precursors of storage proteins can not exit and abnormally accumulated in the ER lumen. To further reveal mechanism underlying MAG2-relating ER-Golgi vesicle transport, we made double mutant of MAG2 and its homolog protein-MAG2-Like (MAL). We found that in addition to more serious defects on vesicle transport, mag2mal mutant is defective on growth and development. The plant is dwarf, having shorter roots and more shoot branches. These suggest that defects on ER-Golgi transport affect growth and development of plant. In this project, we plan to detect level and distribution of auxin, and expression and localization of the auxin transporters, PINs and PILSs, in mag2mal. We also plan to observe morphology of the ER and Golgi apparatus and evaluate efficiency of ER-Golgi transport. Combining the results, it is expected to reveal the correlations between ER-Golgi vesicle transport and plant growth and development.

膜泡运输是细胞各项生命活动的基础。我们在前期研究中发现拟南芥MAG2与MIP1,2,3形成拴留复合体，在ER-Golgi逆向运输中调控运输囊泡与内质网的融合[1,2]。这些基因缺失使内质网向外部的运输受阻，造成储藏蛋白质前体不能有效运离而蓄积在内质网中。为了进一步探究MAG2相关的ER-Golgi膜泡运输机制，我们制作了MAG2和同源蛋白MAG2-Like(MAL)的双重突变体，发现其不仅膜泡运输受到更大影响，而且生长发育受到严重抑制，产生矮小、分枝多、根系不发达等表型缺陷，暗示ER-Golgi膜泡运输障碍影响植物生长发育。本项研究计划检测mag2mal的生长素水平和分布以及生长素转运蛋白PIN和PILS的表达量和定位，同时观察双突变体内质网和高尔基体形态和功能变化并评定ER-Dolgi膜泡运输效率。将研究结果有机地结合进行分析，初步揭示膜泡运输与植物生长发育的相关性。

真核细胞内物质运输主要由膜泡运输完成。我们在前期研究中发现拟南芥MAG2与MIP1,2,3形成拴留复合体，在ER-Golgi运输中调控运输囊泡与内质网的锚定与融合过程。这些基因缺失使内质网运离步骤受阻，造成储藏蛋白质前体积累在内质网中。为了进一步探究MAG2相关的ER-Golgi膜泡运输机制，我们探讨了MAG2的同源蛋白MAG2-Like (MAL)的功能，并制作了MAG2和MAL、MIP2和MIP3、MAG2和MIP3的双重突变体，发现双突变体不仅膜泡运输受到更大影响、储藏蛋白质前体积累更加严重，植物生长发育也受到严重抑制。而且，mag2-1 mal-1的生长素水平显著下降、生长素转运蛋白PIN1、PIN2和PIN3的表达量和分布发生明显变化，植物株高变矮、主根变短、侧根增长，生物量和收获下降。这些结果说明MAG2复合体和MAL在膜泡运输和植物生长发育过程中起重要的调控作用。mag2-1mal-1、mag2-1mip3-1、mip2-1mip3-1双突变体以及相应的单突变体植物不仅发育受到影响，而且对盐胁迫、渗透胁迫等的应答也发生变化。另外，这些突变体的ABA信号通路也受到影响，ABA应答发生变化；反过来，ABA合成和信号通路突变体的囊泡运输受阻严重，暗示二者之间存在密切相关性，我们正在深入探讨。