Cold shock protein 3 plays a negative role in apple drought tolerance by regulating oxidative stress response

Genome-wide identification of cold shock proteins (CSPs) in sweet cherry (Prunus avium L.) and exploring the differential responses of PavCSP1 and PavCSP3 to low temperature and salt stress

BACKGROUND

Cold shock proteins (CSPs) are ubiquitous nucleic acid-binding proteins involved in growth, development, and stress response across various organisms. While extensively studied in many species, their regulatory roles in sweet cherry (Prunus avium L.) remain unclear.

OBJECTIVE

To identify and analyze CSP genes (PavCSPs) in sweet cherry genome, and explore the differential responses of PavCSP1 and PavCSP3 to low temperature and salt stress.

METHODS

Three methods were employed to identify and characterize CSP in sweet cherry genomes. To explore the potential functions and evolutionary relationships of sweet cherry CSP proteins, sequence alignment and phylogenetic tree incorporating genes from five species were conducted and constructed, respectively. To investigate the responses to abiotic stresses, cis-acting elements analysis and gene expression patterns to low-temperature and salt stress were examined. Moreover, transgenic yeasts overexpressing PavCSP1 or PavCSP3 were generated and their growth under stress conditions were observed.

RESULTS

In this study, three CSP genes (PavCSPs) were identified and comprehensively analyzed. The quantitative real-time PCR revealed diverse expression patterns, with PavCSP1-3 demonstrating a particular activity in the upper stem and all members were responsive to low-temperature and salt stress. Further investigation demonstrated that transgenic yeasts overexpressing PavCSP1 or PavCSP3 exhibited improved growth states following high-salt and low-temperature stress.

CONCLUSION

These findings elucidated the responses of PavCSP1 and PavCSP3 to salt and low-temperature stresses, laying the groundwork for further functional studies of PavCSPs in response to abiotic stresses.

PbrCSP1, a pollen tube-specific cold shock domain protein, is essential for the growth and cold resistance of pear pollen tubes

Cold shock domain proteins (CSPs), initially identified in Escherichia coli, have been demonstrated to play a positive role in cold resistance. Previous studies in wheat, rice, and Arabidopsis have indicated the functional conservation of CSPs in cold resistance between bacteria and higher plants. However, the biological functions of PbrCSPs in pear pollen tubes, which represent the fragile reproductive organs highly sensitive to low temperature, remain largely unknown. In this study, a total of 22 CSPs were identified in the seven Rosaceae species, with a focus on characterizing four PbrCSPs in pear (Pyrus bretschneideri Rehder). All four PbrCSPs were structurally conserved and responsive to the abiotic stresses, such as cold, high osmotic, and abscisic acid (ABA) treatments. PbrCSP1, which is specifically expressed in pear pollen tubes, was selected for further research. PbrCSP1 was localized in both the cytoplasm and nucleus. Suppressing the expression of PbrCSP1 significantly inhibited the pollen tube growth in vitro. Conversely, overexpression of PbrCSP1 promoted the growth of pear pollen tubes under the normal condition and, notably, under the cold environment at 4 °C. These findings highlight an essential role of PbrCSP1 in facilitating the normal growth and enhancing cold resistance in pear pollen tubes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-024-01457-w.

Positive regulation of ABA signaling by MdCPK4 interacting with and phosphorylating MdPYL2/12 in Arabidopsis

The phytohormone abscisic acid (ABA) regulates plant growth and development and stress resistance through the ABA receptor PYLs. To date, no interaction between CPK and PYL has been reported, even in Arabidopsis and rice. In this study, we found that MdCPK4 from Malus domestica (Md for short) interacts with two MdPYLs, MdPYL2/12, in the nucleus and the cytoplasm in vivo and phosphorylates the latter in vitro as well. Compared with the wild type (WT), the MdCPK4- or MdPYL2/12-overexpressing Arabidopsis lines showed more sensitivity to ABA, and therefore stronger drought resistance. The ABA-related genes (ABF1, ABF2, ABF4, RD29A and SnRK2.2) were significantly upregulated in the overexpressing (OE) lines after ABA treatment. These results indicate that MdCPK4 and MdPYL2/12 act as positive regulators in response to ABA-mediated drought resistance in apple. Our results reveal the relationship between MdCPK4 and MdPYL2/12 in ABA signaling, which will further enrich the molecular mechanism of drought resistance in plants.

The RNA-binding protein MdHYL1 modulates cold tolerance and disease resistance in apple

Apple (Malus domestica) trees often experience various abiotic and biotic stresses. However, due to the long juvenile period of apple and its high degree of genetic heterozygosity, only limited progress has been made in developing cold-hardy and disease-resistant cultivars through traditional approaches. Numerous studies reveal that biotechnology is a feasible approach to improve stress tolerance in woody perennial plants. HYPONASTIC LEAVES1 (HYL1), a double-stranded RNA-binding protein, is a key regulator involved in apple drought stress response. However, whether HYL1 participates in apple cold response and pathogen resistance remains unknown. In this study, we revealed that MdHYL1 plays a positive role in cold tolerance and pathogen resistance in apple. MdHYL1 acted upstream to positively regulate freezing tolerance and Alternaria alternata resistance by positively modulating transcripts of MdMYB88 and MdMYB124 in response to cold stress or A. alternata infection. In addition, MdHYL1 regulated the biogenesis of several miRNAs responsive to cold and A. alternata infection in apple. Furthermore, we identified Mdm-miRNA156 (Mdm-miR156) as a negative regulator of cold tolerance and Mdm-miRNA172 (Mdm-miR172) as a positive regulator of cold tolerance, and that Mdm-miRNA160 (Mdm-miR160) decreased plant resistance to infection by A. alternata. In summary, we highlight the molecular role of MdHYL1 regarding cold tolerance and A. alternata infection resistance, thereby providing candidate genes for breeding apple with freezing tolerance and A. alternata resistance using biotechnology.

Advances in the Research on Plant WRKY Transcription Factors Responsive to External Stresses

The WRKY transcription factors are a class of transcriptional regulators that are ubiquitous in plants, wherein they play key roles in various physiological activities, including responses to stress. Specifically, WRKY transcription factors mediate plant responses to biotic and abiotic stresses through the binding of their conserved domain to the W-box element of the target gene promoter and the subsequent activation or inhibition of transcription (self-regulation or cross-regulation). In this review, the progress in the research on the regulatory effects of WRKY transcription factors on plant responses to external stresses is summarized, with a particular focus on the structural characteristics, classifications, biological functions, effects on plant secondary metabolism, regulatory networks, and other aspects of WRKY transcription factors. Future research and prospects in this field are also proposed.