Search

Cold stress is a prominent abiotic factor that adversely affects the growth and yield of pears, consequently restricting the cultivation range and resulting in substantial economic losses for the pear industry. Basic region–leucine zipper (bZIP) transcription factors are widely involved in multiple physiological and biochemical activities of plants, particularly in response to cold stress. In this study, the responsiveness of PbbZIP11 in pear to cold stress was investigated, and its role was explored by using pear callus and Arabidopsis thaliana. The findings revealed that overexpression of PbbZIP11 enhanced the tolerance of pear callus and Arabidopsis thaliana to cold stress. The antioxidant enzyme activities of transgenic plants were enhanced and the expression of C-repeat binding transcription factor (CBF) genes was increased as compared to wild-type plants. To better understand the biological function of PbbZIP11, mRNAs were isolated from overexpressed and wild-type Arabidopsis thaliana after cold stress for whole-genome sequencing. The results showed that the expression of some CBF downstream target genes changed after exposure to cold stress. The results suggested that the PbbZIP11 gene could participate in cold-stress signaling through the CBF-dependent pathway, which provides a theoretical basis for the PbbZIP11-mediated response to cold stress and for the genetic breeding of pear varieties with low-temperature tolerance. [ABSTRACT FROM AUTHOR]

Iron is an essential trace element for plants; however, low bioactive Fe in soil continuously places plants in an Fe-deficient environment, triggering oxidative damage. To cope with this, plants make a series of alterations to increase Fe acquisition; however, this regulatory network needs further investigation. In this study, we found notably decreased indoleacetic acid (IAA) content in chlorotic pear (Pyrus bretschneideri Rehd.) leaves caused by Fe deficiency. Furthermore, IAA treatment slightly induced regreening by increasing chlorophyll synthesis and Fe2+ accumulation. At that point, we identified PbrSAUR72 as a key negative effector output of auxin signaling and established its close relationship to Fe deficiency. Furthermore, the transient PbrSAUR72 overexpression could form regreening spots with increased IAA and Fe2+ content in chlorotic pear leaves, whereas its transient silencing does the opposite in normal pear leaves. In addition, cytoplasm-localized PbrSAUR72 exhibits root expression preferences and displays high homology to AtSAUR40/72. This promotes salt tolerance in plants, indicating a putative role for PbrSAUR72 in abiotic stress responses. Indeed, transgenic plants of Solanum lycopersicum and Arabidopsis thaliana overexpressing PbrSAUR72 displayed less sensitivity to Fe deficiency, accompanied by substantially elevated expression of Fe-induced genes, such as FER/FIT, HA, and bHLH39/100. These result in higher ferric chelate reductase and root pH acidification activities, thereby hastening Fe absorption in transgenic plants under an Fe-deficient condition. Moreover, the ectopic overexpression of PbrSAUR72 inhibited reactive oxygen species production in response to Fe deficiency. These findings contribute to a new understanding of PbrSAURs and its involvement in Fe deficiency, providing new insights for the further study of the regulatory mechanisms underlying the Fe deficiency response. [ABSTRACT FROM AUTHOR]

Russeting, a disorder of pear fruit skin, is mainly caused by suberin accumulation on the inner part of the outer epidermal cell layers. ABA was identified as a crucial phytohormone in suberification. Here, we demonstrated that the ABA content in russet pear skin was higher than in green skin. Then, ABA was applied to explore the changes in phenotype and suberin composition coupled with RNA-Seq and metabolomics to investigate the probably regulatory pathway of ABA-mediated suberification. The results showed that ABA treatment increased the expression of ω-3 fatty acid desaturase (FAD) and the content of α-linolenic acid. We identified 17 PbFADs in white pear, and the expression of PbFAD3a was induced by ABA. In addition, the role of PbFAD3a in promoting suberification has been demonstrated by overexpression in Arabidopsis and VIGS assays in the fruitlets. GUS staining indicated that the promoter of PbFAD3a was activated by ABA. Furthermore, MYC2 and MYB1R1 have been shown to bind to the PbFAD3a promoter directly and this was induced by ABA via yeast one-hybrid (Y1H) screening and qRT–PCR. In summary, our study found that ABA induces the expression of MYC2 and MYB1R1 and activates the PbFAD3a promoter, contributing to the formation of russet pear skin. Functional identification of key transcription factors will be the goal of future research. These findings reveal the molecular mechanism of ABA-mediated suberization in the russet skin and provide a good foundation for future studies on the formation of russet skin. [ABSTRACT FROM AUTHOR]

• The skin dynamics development of two pear cultivars and their mutants were analyzed. • The key genes and metabolites involved in russet skin formation were identified. • A set of TFs was predicted as putative regulators of russet skin formation. • We emphasis on exploring the underlying mechanisms of russet pear skin formation. Different periderm development makes the partial and full russet skin of pear fruit, which negatively influence pear fruit appearance quality. The switch gene for russet skin formation and the functional conservation of the homologs among different species showed to have multiple significance to clarify the transcriptional network underlying russet skin formation. In this study, two pear cultivars coupled with their mutants were used to explore the underlying molecular regulatory network of russet skin formation. RNA-sequencing and metabolomics were used to identify the key pathways and switch genes involved in russet skin formation, and identified genes involved in lignin biosynthesis, suberin biosynthesis, and suberin transporters. Additionally, a set of transcription factors was identified via coexpression network analysis and differential expression analysis, including PbMYB308, PbbHLH49, PbWRKY24 , and PbNAC40 , which had a high correlation with russet skin-related genes. These genes were predicted as putative regulators involved in russet pear skin formation. qRT–PCR was performed to validate the transcriptome data. Two varieties and their mutants were used for the first time to explore the switch genes and underlying mechanisms of russet formation. We concentrated on the russet skin development in pear fruit, with an emphasis on exploring the underlying regulatory mechanisms. [ABSTRACT FROM AUTHOR]