Jiang Guoxiang, Yan Huiling, Wu Fuwang, Zhang Dandan, Zeng Wei, Qu Hongxia, Chen Feng, Tan Li, Duan Xuewu, Jiang Yueming
Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.
University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, China.
Plant Cell Physiol. 2017 Jun 1;58(6):1075-1089. doi: 10.1093/pcp/pcx054.
Senescence is a key factor resulting in deterioration of non-climacteric fruit. NAC transcription factors are important regulators in plant development and abiotic stress responses, yet little information regarding the role of NACs in regulating non-climacteric fruit senescence is available. In this study, we cloned 13 NAC genes from litchi (Litchi chinensis) fruit, and analyzed subcellular localization and expression profiles of these genes during post-harvest natural and low-temperature-delayed senescence. Of the 13 NAC genes, expression of LcNAC1 was up-regulated in the pericarp and pulp as senescence progressed, and was significantly higher in senescence-delayed fruit than that in naturally senescent fruit. LcNAC1 was induced by exogenous ABA and hydrogen peroxide. Yeast one-hybrid analysis and transient dual-luciferase reporter assay showed that LcNAC1 was positively regulated by the LcMYC2 transcription factor. LcNAC1 activated the expression of LcAOX1a, a gene associated with reactive oxygen species regulation and energy metabolism, whereas LcWRKY1 repressed LcAOX1a expression. In addition, LcNAC1 interacted with LcWRKY1 in vitro and in vivo. These results indicated that LcNAC1 and LcWRKY1 form a complex to regulate the expression of LcAOX1a antagonistically. Taken together, the results reveal a hierarchical and co-ordinated regulatory network in senescence of harvested litchi fruit.
衰老是非跃变型果实品质劣变的关键因素。NAC转录因子是植物发育和非生物胁迫响应中的重要调节因子，然而关于NAC在调控非跃变型果实衰老方面的作用，目前所知甚少。在本研究中，我们从荔枝果实中克隆了13个NAC基因，并分析了这些基因在采后自然衰老和低温延迟衰老过程中的亚细胞定位及表达谱。在这13个NAC基因中，随着衰老进程，LcNAC1在果皮和果肉中的表达上调，且在衰老延迟的果实中显著高于自然衰老的果实。LcNAC1受外源脱落酸和过氧化氢诱导。酵母单杂交分析和瞬时双荧光素酶报告基因检测表明，LcNAC1受LcMYC2转录因子正向调控。LcNAC1激活了与活性氧调控和能量代谢相关的基因LcAOX1a的表达，而LcWRKY1抑制LcAOX1a的表达。此外，LcNAC1在体外和体内均与LcWRKY1相互作用。这些结果表明，LcNAC1和LcWRKY1形成复合物，拮抗调控LcAOX1a的表达。综上所述，这些结果揭示了采后荔枝果实衰老过程中的一个分级协调调控网络。
