PbrmiR397a regulates lignification during stone cell development in pear fruit

First author: Cheng Xue; Affiliations: Nanjing Agricultural University (南京农业大学): Nanjing, China

Corresponding author: Jun Wu

Lignified (木质化的) stone cells substantially reduce fruit quality. Therefore, it is desirable to inhibit stone cell development by using genetic technologies. However, the molecular mechanisms regulating lignification are poorly understood in fruit stone cells. In this study, we have shown that microRNA (miR) miR397a regulates fruit cell lignification by inhibiting laccase (LAC; 漆酶) genes that encode key lignin biosynthesis enzymes. Transient overexpression of PbrmiR397a, which is the miR397a of Chinese pear (Pyrus bretschneideri), and simultaneous silencing of three LACgenes reduced the lignin content and stone cell number in pear fruit. A single nucleotide polymorphism (SNP) identified in the promoter of the PbrmiR397agene was found to associate with low levels of fruit lignin, after analysis of the genome sequences of sixty pear varieties. This SNP created a TCA‐element that responded to salicylic acid (SA) to induce gene expression as confirmed using a cell‐ased assay system. Furthermore, stable overexpression of PbrmiR397ain transgenic tobacco plants reduced the expression of target LACgenes and decreased the content of lignin but did not change the ratio of syringyl and guaiacyl (紫丁香基和愈疮木基) lignin monomers. Consistent with reduction of lignin content, the transgenic plants showed fewer numbers of vessel elements (导管分子) and thinner secondary walls in the remaining elements compared to wild‐ ype control plants. This study has advanced our understanding of the regulation of lignin biosynthesis and provided useful molecular genetic information for improving pear fruit quality.

木质化的石细胞会极大的降低水果果实的品质。因此，对于通过遗传学的方法抑制石细胞发育的需求较为迫切。然而，目前对于水果石细胞中木质化调控的分子机制还所知不多。本文的研究显示miR397a通过抑制木质素生物合成关键酶漆酶LAC的表达来调控水果细胞的木质化。过表达中国梨的PbrmiR397a基因和同时沉默三个LAC基因会减少水果中木质素的含量以及石细胞的数量。作者通过对60个梨品种的基因组序列分析鉴定到了PbrmiR397a基因启动子区上一个SNP与低的水果木质素含量相关。作者进一步通过基于细胞的试验系统表明该SNP形成一个TCA元件，能够响应水杨酸，诱导基因的表达。此外，在转基因烟草中过表达PbrmiR397a能够减少LAC基因的表达，并降低木质素的含量，但并不改变紫丁香基和愈疮木基木质素单体的比例。与降低的木质素含量一致，转基因植株导管分子数量更少，并且与野生型相比，其余元件的次生细胞壁更加薄弱。本文的研究拓宽了我们对于木质素生物合成调控分子机制的认知，同时也为将来水果果实的遗传改良提供了有效的分子遗传基础。

通讯：吴俊 (http://onlinelibrary.wiley.com/doi/10.1111/tpj.13666/full)

个人简介：1993.9-1997.6，安徽农业大学园艺学院，园艺专业学士；1997.9-2000.6，安徽农业大学园艺学院，果树学专业硕士；2000.9-2003.6，山东农业大学园艺科学与工程学院，果树学专业博士；2003.7-2005.12，南京农业大学园艺学院，讲师；2005.3-2008.9，南京农业大学，果树学博士后；2006.1-2010.12，南京农业大学园艺学院，副教授；2010.2-2011.2，美国伊利诺伊大学香槟校区，访问学者；2011.1-2012.12，南京农业大学，园艺学院/作物遗传与种质创新国家重点实验室，教授四级；2013.1-至今南京农业大学，园艺学院/作物遗传与种质创新国家重点实验室，破格教授三级。

研究方向：果树种质资源与分子育种。主要从事梨的基因组进化、优异资源挖掘与利用、以及分子辅助育种技术等方面的研究。

doi: https://doi.org/10.1111/pbi.12950

Journal: Plant Biotechnology Journal

First Published date: 13 May, 2018

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