拟南芥NatA复合体在胚胎发育中的作用及分子机制研究

NatA complex is a kind of N-terminal acetyltransferase complex that transfers an acetyl group from Ac-CoA to the α-amino group of the first amino acid residue of a protein, which in turn affects protein functions. NatA complex establishes a link between cellular metabolism and the regulation of protein function, which increases the regulation accuracy and breadth of life activities. Our previous studies revealed that mutation of Naa10, which encoding the catalytic subunit of the NatA complex in Arabidopsis, leads to delayed embryo development, abnormal cell division of hypophysis, ectopic distribution of auxin and eventually irregular and lethal globular embryo. Wild-type Naa10 can rescue the embryonic lethal phenotype of the mutant. In this project, we will take advantage of the mutants of Naa10 and Naa15, which encoding the catalytic and auxiliary subunit of the NatA complex in Arabidopsis respectively. By means of a series of molecular, biochemical and genetic methods, we will further study the function and molecular mechanism of NatA complex in the embryonic development, and explain how NatA complex affects the functions of the substrate proteins through Nt-acetylation and in turn regulate embryogenesis. This study will provide new theoretical basis for seed development.

NatA复合体是一种N末端乙酰转移酶复合体，通过把乙酰辅酶A作为乙酰基团的供体，对底物N末端氨基酸的α氨基进行乙酰化修饰进而影响蛋白功能。该复合体将体内代谢状态与蛋白功能调控联系起来，增加了生命活动调控的精度和广度。我们前期研究发现，在拟南芥NatA复合体的催化亚基Naa10的基因突变体中，胚胎发育延滞，胚根原细胞异常分裂，生长素的分布异常，最终产生无规则的球状胚，表现为胚胎致死；野生型Naa10可以恢复突变体胚胎致死的表型。本研究拟以NatA复合体的催化亚基Naa10和辅助亚基Naa15的基因突变体为模型，通过胚胎透明、生长素动态分布的观察、生长素极性运输蛋白定位的观察、原位杂交、NatA复合体底物筛选、IP-MS等技术，进一步研究NatA复合体调控胚胎发育的作用及分子机制，阐明NatA复合体是如何通过Nt乙酰化修饰影响底物蛋白功能进而调控胚胎发育进程的，为种子发育调控提供新的理论依据。

N末端乙酰转移酶以乙酰辅酶A作为乙酰基团的供体，对底物蛋白N末端α氨基进行乙酰化修饰进而调控蛋白功能。该修饰将体内代谢状态与蛋白功能调控联系起来，增加了生命活动调控的精度和广度。本项目研究结果表明拟南芥N末端乙酰转移酶复合体NatA组分Naa10和Naa15缺失导致胚胎发育迟缓，胚体和胚柄细胞分裂异常，最终造成胚胎致死。Naa10和Naa15通过调控生长素极性运输蛋白PIN1的定位，进而维持生长素的极性分布，最终调控胚胎和胚柄的正常发育进程。此外，NatA复合体的组分Naa50缺失表现为主根变短，根尖分生区变短，分生区特异表达蛋白PLT1/2表达范围变小；表皮细胞异常膨大并且提前分化出根毛；皮层、内皮层和中柱鞘细胞异常纵向分裂；细胞出现随机的死亡，表明Naa50通过维持根尖细胞的细胞属性和生理活性，进而维持根的正常生长发育。此研究将丰富种子发育和根发育调控的机制。