Msr介导的NAC转录因子亚砜化调节参与调控香蕉果实采后衰老的机制研究

Study on the regulation of transcription factors in plants involves phosphorylation, ubiquitination, SUMO, methylation and acetylation. However, little information on regulation of transcription factor sulfoxidation (reversible oxidation of methionine residues) is available. Methionine sulfoxide reductase (Msr) plays an important role in delaying aging and resistance to oxidative stress by repairing the oxidized methionine resides in proteins. Our previous study showed that MaNAC42, a senescence-related transcription factor in banana fruit, possibly was the target of MaMsrB2. In this project, the mechanism of fruit ripening and senescence were studied from the perspective of the regulation of sulfoxidation of NAC transcription factor on the expression of senescence-related genes. The following issues will be studied: the senescence characteristics of postharvest banana fruit; the redox regulatory mechanism of MaNAC42 transcription factor by MaMsrB2; Identification of the target genes of MaNAC42; the involvement of MaMsrB2-mediated redox modification of MaNAC42 in regulating the expression of senescence-related genes. The results of the project have important significance for revealing the mechanism of postharvest fruit senescence and will provide a theoretical basis for prolonging fruit storage and transportation period and reducing postharvest losses, and thereby improving fruit industry economy benefit.

植物中转录因子的调控主要涉及磷酸化、泛素化、SUMO化、甲基化、乙酰化等，目前并无亚砜化[甲硫氨酸(Met)残基可逆性氧化]调控的报道。甲硫氨酸亚砜还原酶（Msr）能修复被氧化的蛋白质Met残基，在延缓生物体衰老和响应氧化胁迫中发挥重要作用。我们前期的研究发现，香蕉果实中与成熟衰老相关的转录因子MaNAC42可能为MaMsrB2的目标蛋白。本项目以香蕉果实为材料，拟从NAC转录因子亚砜化修饰对衰老相关基因表达调控的角度，研究果实采后成熟衰老的机理及调控机制。主要内容包括：分析香蕉果实采后衰老特性；解析香蕉MaMsrB2对MaNAC42的氧化还原调控机制；鉴别香蕉果实中MaNAC42的靶标基因；验证MaMsrB2介导的MaNAC42氧化还原调节参与调控香蕉采后衰老相关基因的转录。研究结果对于深入揭示采后水果衰老机理具有重要意义，将为研发保鲜技术以延长果实贮运期和降低采后损耗提供理论依据。

我国是世界第一大水果生产国，但采后损失严重，高达20-30%。当前限制水果保鲜关键新技术研发的最主要因素是对果实衰老和品质劣变相关的关键基础理论仍缺乏深层次的认识。生物大分子氧化是导致机体衰老的重要的因素。甲硫氨酸亚砜还原酶（Msr）是一类还原蛋白中被氧化的甲硫氨酸的酶，Msr介导的氧化修复可能参与生物体衰老的调控，但相关研究主要与慢性疾病的和氧化应激相关。本项目以呼吸跃变型果实香蕉和番茄为研究对象，运用生物化学、分子生物学和遗传学手段，从Msr在氧化蛋白修复和功能调控角度，阐明了Msr介导转录因子NAC转录因子的氧化还原修饰在香蕉和番茄采后衰老和劣变的机理。获得的重要结果如下：1）明确了香蕉和番茄果实在成熟和胁迫条件下蛋白氧化特性和Msr基因表达特性；2）证实了香蕉果实中MaMsrB2与MaNAC42的互作以及番茄果实中MsrE4/MsrB2与NOR的互作；3）鉴定出香蕉果实中MaNAC42的目标基因；4）体外证实了MaMsrB2对MaNAC42以及MsrE4/MsrB2对NOR氧化还原状态、DNA结合特性和转录活性的调控作用；5）分析了模拟MaNAC42和NOR亚砜化对其DNA结合能力和转录活性的影响； 6）解析了NOR亚砜化对番茄果实的成熟的调控作用及作用机制。该项目研究成果有助于进一步了解热带、亚热带水果采后衰老的机理及其控制机制，为进一步研发控制果实衰老的贮运技术提供新的思路。本项目发表SCI收录论文16篇；获授权发明专利6件（其中美国专利1件）；培养博士后1名，博士研究生3名。