III型AtOFPs转录因子对拟南芥荚果形态的调控

In Arabidopsis, there are 18 genes encoding Arabidopsis thaliana Ovate Family Proteins (AtOFPs). A couple of years ago, we identified AtOFPs as a novel transcription repressor family and found that AtOFPs regulate multiple aspects of plant growth and development including tissue and organ morphogenesis, however, the mechanisms underlining the functions of AtOFPs remain largely unknown. All the AtOFPs mutants identified so far including Atofp1, Atofp4, Atofp8, Atofp10, Atofp15 and Atofp16 single mutants, and Atofp1 Atofp4 and Atofp15 Atofp16 double mutants are morphologically similar to wild type plants, however, plants overexpressing AtOFPs displayed a number of abnormal phenotypes, which could be categorized into three distinct classes, indicating that AtOFPs have overlapping and diverse functions in regulating plant growth and development. Accordingly, AtOFPs were categorized into three classes, Class I, II and III AtOFPs. Plants overexpressing any of the four Class III AtOFPs genes including AtOFP13, AtOFP15, AtOFP16 and AtOFP18 have blunt-ended siliques, a phenotype that was also observed in er, a mutant of the receptor like protein kinase gene ERECTA (ER), and overexpression of ER in AtOFP15 or AtOFP16 overexpressing plants restored their blunt-ended siliques phenotypes. These results suggest that Class III AtOFPs and ER may work in the same signaling pathway in regulating silique morphology. ER has been shown to regulate plant growth and development through mitogen-activated protein kinase (MAPK) cascades, the universal signal transduction modules in eukaryotes including plants. MAPK cascades mediate intracellular transmission and amplification of extracellular stimuli through sequential protein phosphorylation, and both AOFP15 and AtOFP16 have predicated MAPK phosphorylation sites, so it is like MAPK cascades mediated protein phosphorylation also involved in Class III AtOFPs regulated silique morphology. In this proposal, a combination of plant molecular biology, genetics, biochemistry and bioinformatics approaches going to be use to study the mechanisms underneath the regulation of silique morphology by Class III AtOFPs transcription factor AtOFP15 and AtOFP16. Proposed studies include but may not limited to dissection of the relationship between Class III AtOFPs and ER, identification of target genes of Class III AtOFPs transcription factors, examination of the protein phosphorylation of Class III AtOFPs and test of the potential effects of protein phosphorylation on the transctiptional activities of Class III AtOFPs. Results gain from the proposed studies will enhance our knowledge of the regulation of plant tissue and organ morphogenesis by AtOFPs, and may lead to the improvement of crop quality by modification of AtOFP genes.

拟南芥卵形蛋白家族（AtOFPs）是申请者发现的一个新型的转录抑制因子家族，可以调控植物多种器官的形态，但其作用机理尚不清楚。基于转基因植株表型差异，我们将AtOFPs分为3种类型，其中III型 AtOFPs过表达植株具有平末端荚果，与类受体蛋白激酶基因突变体er表型类似，且可被过表达ER所恢复，而ER已被证明可通过促分裂原活化蛋白激酶（MAPK）级联途径调控植物的生长发育。在此基础上，本项目拟综合利用分子生物学、遗传学、生物信息学等学科的技术和方法，以III型AtOFPs转录因子AtOFP15和16为主，从分析其与ER在调控荚果形态中的关系，鉴定其靶基因，探究MAPK级联途径是否参与调控其蛋白磷酸化等三个方面解析III型AtOFPs转录因子调控拟南芥荚果形态的机理。研究结果将丰富AtOFPs调控植物组织器官形态的作用机制的理论知识，为利用卵形蛋白家族基因进行农作物的性状改良提供理论依据。

拟南芥卵形蛋白家族（Arabidopsis thaliana Ovate Family Proteins，AtOFPs）是一个由申请者首先发现的、植物特有、新型的转录抑制因子家族。我们前期的研究发现AtOFPs可以调控植物生长发育的多个方面。根据过表达AtOFPs基因导致的转基因植株表型的不同，我们将AtOFPs分为3个不同类型，其中OFP13，OFP15，OFP16和OFP18属于III型AtOFPs。过表达III型AtOFPs基因的转基因植株的一个共同的典型特征是其荚果具有平末端，类受体蛋白激酶基因突变体erecta (er) 也具有类似的表型，而ER能够通过促分裂原活化蛋白激酶（Mitogen-activated Protein Kinase, MAPK）级联途径调控植物的生长发育，暗示III型AtOFPs和ER可能作用于同一信号途径调控植物的生长发育。本项的目的就是在这些研究的基础上，综合利用分子生物学、遗传学、生物信息学等学科的技术和方法，研究III型AtOFPs和ER在调控植物生长发育中的关系，进而解析III型AtOFPs转录因子调控拟南芥荚果形态的机理。通过本项目的研究，我们发现：① ER作用于III型AtOFPs转录因子的上游调控拟南芥荚果形态，但ER和III型AtOFPs可能作用于不同的途径调控植物生长发育的其它方面；② MAPK磷酸化位点磷酸化状态对III型AtOFPs转录因子的转录抑制活性影响较小，但影响其对拟南芥荚果形态的调控，说明ER介导的蛋白磷酸化信号途径能够影响III型AtOFPs转录因子的功能；③ OFP15和OFP16是主动抑制子，但OFP18是被动抑制子，说明虽然都具有转录抑制活性，但III型AtOFPs不同成员的转录抑制作用的机制可能不同；④ III型AtOFPs基因的表达也受到ER介导的蛋白磷酸化信号途径的影响。上述研究的主要结果均已发表，迄今共在Frontiers in Plant Science、Journal of Plant Interactions、BMC Plant Biology和Plant Science等SCI杂志上发表论文9篇。