Abstract
BackgroundThe 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).ResultsIn 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.
Highlights
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
Subcellular localization of PbrPUBs were predicted by Cell-PLoc 2.0, and we found that most PUB proteins were located on cell nucleus, except six located in cytoplasm and three located in cell membrane (Table 1)
In our study, a total of 62 PbrPUB members were identified in Chinese white pear (Pyrus bretschneideri) genome, and were unevenly distributed on 17 pear chromosomes
Summary
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. Several stresses often lead to oxidative damage and have adverse impacts on plant growth and. The central component of UPS is the highly conserved, 76 amino acid protein ubiquitin. E3 enzymes are clearly the key factors that define substrate specificity. According to their reaction mechanism and subunit compositions, four main types were classified: Ubox, HECT (Homology to E6-Associated Carboxy-Terminus), RING (Really Interesting New Gene) and Cullin–RING ligases (CRLs) [4]. U-box ubiquitin ligases are characterized by a conserved U-box motif of about 70 amino acids. U-box ubiquitin ligases were firstly discovered among E3 ubiquitin ligases, and was first clarified from ubiquitin fusion degradation protein-2 (UFD2) in yeast [9]
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