Center of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, 210095, China.
BMC Plant Biol. 2021 May 26;21(1):235. doi: 10.1186/s12870-021-03024-3.
The plant U-box (PUB) proteins are a family of ubiquitin ligases (E3) enzymes that involved in diverse biological processes, as well as in responses to plant stress response. However, the characteristics and functional divergence of the PUB gene family have not yet been previously studied in the Chinese white pear (Pyrus bretschneideri).
In the present study, we identified 62 PbrPUBs in Chinese white pear genome. Based on the phylogenetic relationship, 62 PUB genes were clustered into five groups. The results of conserved motif and gene structure analysis supported the classification phylogenetic tree. The PbrPUB genes were unevenly distribution on 17 pear chromosomes, chromosome 15 housed most member of PUB family, with eight PUB genes. Cis-acting element analysis indicated that PUB genes might participate in diverse biological processes, especially in the response to abiotic stresses. Based on RNA-data from 'Dangshansuli' at seven tissues, we found that PUB genes exhibited diverse of expression level in seven tissues, and qRT-PCR experiment further supported the reliable of RNA-Seq data. To identify candidate genes associated with resistance, we conducted qRT-PCR experiment the expression level of pear seed plant under four abiotic stresses, including: ABA, dehydration, salt and cold treatment. One candidate PUB gene associated with dehydration stress was selected to conduct further functional experiment. Subcellular localization revealed PbrPUB18 protein was located on cell nucleus. Furthermore, heterologous over-expression of PbrPUB18 in Arabidopsis indicated that the over-expression of PbrPUB18 could enhance resistance in drought treatment. In conclusions, we systematically identified the PUB genes in pear, and provided useful knowledge for functional identification of PUB genes in pear.
植物 U-box（PUB）蛋白是一类泛素连接酶（E3）酶，参与多种生物过程，以及植物应激反应。然而，PUB 基因家族的特征和功能分化在中华白梨（Pyrus bretschneideri）中尚未得到研究。
本研究在中华白梨基因组中鉴定了 62 个 PbrPUBs。基于系统发育关系，将 62 个 PUB 基因聚类为 5 个组。保守基序和基因结构分析的结果支持了分类系统发育树。PbrPUB 基因在 17 条梨染色体上不均匀分布，15 号染色体上有 8 个 PUB 基因，包含最多的 PUB 家族成员。顺式作用元件分析表明，PUB 基因可能参与多种生物过程，特别是对非生物胁迫的反应。基于“Dangshansuli”在 7 种组织中的 RNA 数据，我们发现 PUB 基因在 7 种组织中表现出不同的表达水平，qRT-PCR 实验进一步支持了 RNA-Seq 数据的可靠性。为了鉴定与抗性相关的候选基因，我们对梨种子在四种非生物胁迫下（ABA、干旱、盐和冷处理）的表达水平进行了 qRT-PCR 实验。选择一个与干旱胁迫相关的候选 PUB 基因进行进一步的功能实验。亚细胞定位显示 PbrPUB18 蛋白位于细胞核。此外，在拟南芥中过表达 PbrPUB18 表明，过表达 PbrPUB18 可以增强其对干旱处理的抗性。总之，我们系统地鉴定了梨中的 PUB 基因，为梨 PUB 基因的功能鉴定提供了有用的知识。
