番茄果皮网状裂纹控制基因的克隆及机理解析

Fruit-cracking seriously affects tomato appearance quality and commodity quality. At present, controlling the environmental condition is the most usually practice to avoid fruit cracking, but it is little known on the mechanism of fruit cracking. Our previous results showed that the fruit skin of IL4-4 shows up netted-cracking like muskmelon. We have observed the structures of fruit cracking by paraffin section and scanning electron microscope, the results revealed that the netted-cracking began to appear as early at 28DPA, and gradually developed, finally reached to all the surfaces of fruit until 35DPA. In this study, we try to clone this gene by map-based cloning approach by F2 population derived from crossing M82 with IL4-4 and further functionally characterize this gene by transgenic analysis. On this basis, we will determine the regulators, interacting proteins and down-stream targets by Y1H, Y2H, ChIP-seq and transgenic analysis. Finally, we integrate the transcriptional and metabolic results to explore the molecular mechanism of fruit-netted cracking, and develop the molecular markers for fruit cracking selection as well.

裂果严重的影响番茄外观品质和商品品质。生产上主要是通过调控外界环境条件减少裂果，从遗传上对果皮开裂的机理研究甚少。本项目组在前期研究中，发现潘那利番茄渐渗系IL4-4果实表皮出现类似于网纹甜瓜表皮的网状裂纹，通过组织石蜡切片、扫描电镜对表型观察，发现裂纹在番茄膨大期（28DPA）开始出现，到绿熟期（35DPA）遍布整个果实表面。本研究利用番茄栽培种M82与IL4-4杂交构建遗传分离群体，通过图位克隆的方法分离番茄果皮网状裂纹控制基因并鉴定其功能，通过酵母单/双杂交、ChIP-Seq等筛选目的基因的上下游调控基因及互作蛋白并进行转基因验证，结合转录组学研究和代谢组学研究，最终阐明番茄中果皮网状裂纹形成的机理，开发分子标记，为选育番茄抗裂新品种奠定基础。

果实裂果是影响果实完整性并降低番茄和其他肉质水果的商业价值的。本项研究中，我们在番茄IL4-4中发现了一种新的果实网裂（FNC）表型，该表型既不存在于供体母本（LA0716）中，也不存在受体父本（M82）中。为了对FNC基因进行基因鉴定，我们用M82与渐渗系IL4-4杂交，产生了F2分离群体，发现这个显性基因决定了果实网状裂纹的形成。进一步基于图位克隆将 FNC 位点缩小到染色体 4 上的 230 kb 区域。测序和注释分析表明，FNC（Solyc04g082540）是最有可能的候选基因。超量表达FNCAC和FNCIL4-4对FNC的功能表征显示果实网纹裂表型，表明FNC的转录水平导致果网开裂的功能。这些发现得到了FNC正交体在网裂胡椒和甜瓜的进一步证实，表明不同植物物种的共同调控机制。此外，细胞质和细胞核局部FNC表明，参与木质素、脂质、脂质传输和细胞壁代谢的基因表达增加。这些发现为果实裂果开提供了新的遗传见解，并为促进抗裂品种的分子改良提供了前进的道路。