Background 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). Results 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.

Background The basic helix-loop-helix (bHLH) transcription factors play important roles in many processes in plant growth, metabolism and responses to abiotic stresses. Although, the sequence of Chinese white pear genome (cv. ‘Dangshansuli’) has already been reported, there is still a lack of clarity regarding the bHLH family genes and their evolutionary history. Results In this work, a genome-wide identification of the bHLH genes in Chinese white pear was performed, and we characterized the functional roles of these PbrbHLH genes in response to abiotic stresses. Based on the phylogenetic analysis and structural characteristics, 197 identified bHLH genes could be well classified into 21 groups. Expansion of PbrbHLH gene family was mainly driven by WGD and dispersed duplication with the purifying selection from the recent WGD. The functional annotation enrichment showed that the majority of PbrbHLHs were enriched in the GO terms and KEGG pathways involved in responds to stress conditions as TFs. Transcriptomic profiles and qRT-PCR revealed that PbrbHLH7, PbrbHLH8, PbrbHLH128, PbrbHLH160, PbrbHLH161 and PbrbHLH195 were significantly up-regulated under cold and drought treatments. In addition, PbrbHLH195-silenced pear seedlings display significant reduced cold tolerance, exhibiting reduced chlorophyll content, as well as increased electrolyte leakage and concentrations of malondialdehyde and H2O2. Conclusion For the first time, a comprehensive analysis identified the bHLH genes in Chinese white pear and demonstrated that PbrbHLH195 is involved in the production of ROS in response to cold stress, suggesting that members of the PbrbHLH family play an essential role in the stress tolerance of pear.

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Background 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 has not yet been previously studied in the Chinese White Pear (Pyrus bretschneideri). Results In the present study, we identified 62 PbrPUBsin Chinese white pear genome. Based on the phylogenetic relationship, 62 PUB genes were clustered into five groups. The conserved motif and gene structure analysis provided further evidence to support 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 indicted 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 support 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 gene 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 valuable information for the molecular mechanism of PUB genes in pear.

Background: The basic helix-loop-helix (bHLH) transcription factors play important roles in many processes in plant growth, metabolism and responses to abiotic stresses. Although, the sequence of Chinese white pear genome (cv. ‘Dangshansuli’) has already been reported, there is still a lack of clarity regarding the bHLH family genes and their evolutionary history. Results: In this work, a genome-wide identification of the bHLH genes in Chinese white pear was performed, and we characterized the functional roles of these PbrbHLH genes in response to abiotic stresses. Based on the phylogenetic analysis and structural characteristics, 197 identified bHLH genes could be well classified into 21 groups. Expansion of PbrbHLH gene family were mainly driven by WGD and dispersed duplication with the purifying selection from the recent WGD. The functional annotation enrichment showed that the majority of PbrbHLHs were enriched in the GO terms and KEGG pathways involved in responds to stress conditions as TFs. Transcriptomic profiles and qRT-PCR revealed that PbrbHLH7, PbrbHLH8, PbrbHLH116, PbrbHLH128, PbrbHLH160 and PbrbHLH195 were significantly up-regulated under cold and drought treatments. In addition, PbrbHLH195-silenced pear seedlings display significant reduced cold tolerance, exhibiting reduced chlorophyll content, as well as increased Electrolyte leakage and concentrations of malondialdehyde and H2O2.Conclusion: For the first time, a comprehensive analysis identified the bHLH genes in Chinese white pear and demonstrated that PbrbHLH195 is involved in the production of ROS in response to cold stress, suggesting that members of the PbrbHLH family play an essential role in the stress tolerance of pear.