Comparative transcriptome analysis provides insights into the mechanism of pear dwarfing

doi:10.1016/S2095-3119(21)63774-7

摘要/Abstract

摘要：

本研究以‘矮玉香’和‘翠冠’为父母本，通过杂交获得矮化性状的后代（DPP）和乔化表型的后代（APP）。与APP相比，DPP植株高度降低了62.8%，节间长度显著缩短。茎尖组织切片观察显示，DPP细胞形状不规则，细胞平均长度较大，但纵向排布的细胞数量显著减少。两种表型梨之间的交叉嫁接试验表明，‘矮生梨’的矮化表型主要由地上部分决定，与根系无关。根据二者茎尖的RNAseq数据共鉴定出1401个差异表达基因,其中包含101转录因子。功能富集分析显示，植物激素、细胞分裂、细胞壁代谢等相关通路中的基因显著差异表达。在DPP中，若干BR信号转导和细胞周期相关基因表达显著下调；同时，一些调控BR和GA降解的基因表达上调。结合切片观察的结果与RNA-seq的数据推断，DPP的矮化表型主要归因于细胞分裂的不足。为进一步缩小候选基因集，将差异表达基因映射到前人所做的‘Le Nain Vert’矮化性状定位区间，共鉴定出4个关键基因。结合功能注释分析，发现其中一个DELLA基因可能在调控‘矮生梨’矮化表型中发挥重要的作用。本研究结果为进一步探索梨矮化的遗传和分子机制奠定了基础。

Abstract: Dwarfism is an important trait which is closely related to the efficiency of fruit orchard management and production. However, dwarfing cannot be widely applied in the cultivation of pears, especially Asian pears. Developing varieties with dwarf characteristics is a goal of paramount importance in pear breeding. In the present study, dwarf phenotype pears (DPPs) and arborescent phenotype pears (APPs) were obtained from the offspring of a cross between ‘Aiyuxiang’ and ‘Cuiguan’ pear cultivars, which exhibited dwarfed and arborescent statures, respectively. When compared with APPs, the heights of DPPs showed a 62.8% reduction, and the internode lengths were significantly shorter. Cross-grafting between DPPs and APPs demonstrated that the dwarfed phenotype of DPPs was primarily induced by the aerial portions of the plant, and independent of the root system. Observations of stem tissue sections showed that DPP cells were arranged chaotically with irregular shapes, and the average length was larger than that of the APP cells. A total of 1 401 differently expressed genes (DEGs) in shoot apices between DPPs and APPs were identified by RNA-sequencing (RNA-Seq), and these DEGs were mainly enriched in the ‘phytohormone-related pathways, cell wall metabolism and cell division’ categories. Moreover, 101 DEGs were identified as transcription factors (TFs). In DPPs, several brassinosteroids (BR) signaling and cell cycle-related genes were significantly down-regulated, while genes involved in BR and GA degradation were up-regulated. Comprehensive analysis of RNA-Seq data and stem tissue sections suggested that the dwarfed phenotype of DPPs could be primarily attributed to deficiencies in cell division. Previous work using simple sequence repeat (SSR) markers narrowed the location of the gene responsible for the dwarf phenotype of ‘Le Nain Vert’. Through combined analysis of our transcriptomic data with the SSR results, we identified four genes as promising candidates for the dwarf phenotype, among which, a DELLA gene could be the most promising. The results presented in this study provide a sound foundation for further exploration into the genetic and molecular mechanisms underlying pear dwarfing.

Key words: pear , dwarf phenotype , RNA-Seq , cell division , phytohormones

. [J]. Journal of Integrative Agriculture, 2022, 21(7): 1952-1967.

TANG Zi-kai, SUN Man-yi, LI Jia-ming, SONG Bo-bo, LIU Yue-yuan, TIAN Yi-ke, WANG Cai-hong, WU Jun. Comparative transcriptome analysis provides insights into the mechanism of pear dwarfing[J]. Journal of Integrative Agriculture, 2022, 21(7): 1952-1967.

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