Identification of the DcHsp20 gene family in carnation (Dianthus caryophyllus) and functional characterization of DcHsp17.8 in heat tolerance

Genome-wide profile analysis of the Hsp20 family in lettuce and identification of its response to drought stress

Heat shock protein 20 (Hsp20) plays a very important role in response to abiotic stressors such as drought; however, in lettuce (Lactuca sativa L.), this gene family is poorly understood. This study used bioinformatics methods to identify 36 members of the lettuce Hsp20 family, which were named LsHsp20-1~LsHsp20-36. Subcellular localization results revealed that 26 members of the LsHsp20 protein family localized to the cytoplasm and nucleus. Additionally, 15 conserved domains were identified in the LsHsp20 protein family, with the number of amino acids ranging from 8 to 50. Gene structure analysis revealed that 15 genes (41.7%) had no introns, and 20 genes (55.5%) had one intron. The proportion of the LsHsp20 secondary structure was random coil > alpha helix > extended strand > beta turn. Chromosome positioning analysis indicated that 36 genes were unevenly distributed on nine chromosomes, and four pairs of genes were collinear. The Ka/Ks ratio of the collinear genes was less than 1, indicating that purifying selection dominated during L. sativa evolution. Thirteen pairs of genes were collinear in lettuce and Arabidopsis, and 14 pairs of genes were collinear in lettuce and tomato. A total of 36 LsHsp20 proteins were divided into 12 subgroups based on phylogenetic analysis. Three types of cis-acting elements, namely, abiotic and biotic stress-responsive, plant hormone-responsive, and plant development-related elements, were identified in the lettuce LsHsp20 family. qRT-PCR was used to analyze the expression levels of 23 LsHsp20 genes that were significantly upregulated on the 7th or 14th day of drought treatment, and the expression levels of two genes (LsHsp20-12 and LsHsp20-26) were significantly increased by 153-fold and 273-fold on the 14th and 7th days of drought treatment, respectively. The results of this study provide comprehensive information for research on the LsHsp20 gene family in lettuce and lay a solid foundation for further elucidation of Hsp20 biological functions, providing valuable information on the regulatory mechanisms of the LsHsp20 family in lettuce drought resistance.

Comprehensive analysis of Dendrobium catenatum HSP20 family genes and functional characterization of DcHSP20-12 in response to temperature stress

Heat shock proteins (HSPs) are a class of protective proteins in response to abiotic stress in plants, and HSP20 plays an essential role in response to temperature stress. However, there are few studies on HSP20 in Dendrobium catenatum. In this study, 18 DcHSP20 genes were identified from the D. catenatum genome. Phylogenetic analysis showed that DcHSP20s could be classified into six subgroups, each member of which has similar conserved motifs and gene structures. Gene expression analysis of 18 DcHSP20 genes revealed that they exhibited variable expression patterns in different plant tissues. Meanwhile, all 18 DcHSP20 genes were induced to be up-regulated under high temperature, while six genes (DcHSP20-2/9/10/12/16/17) were significantly up-regulated under low temperature. Moreover, combining gene expression under high and low temperature stress, the DcHSP20-12 gene was cloned for functional analysis. The germination ratios, fresh weights, root lengths of two DcHSP20-12-overexpressing transgenic Arabidopsis thaliana lines were significantly higher, but MDA contents were lower than that of wild-type (WT) plants under heat and cold stresses, displayed enhanced thermotolerance and cold-resistance. These results lay a foundation for the functional characterization of DcHSP20s and provide a candidate gene, DcHSP20-12, for improving the tolerance of D. catenatum to temperature stress in the future.

Genome-wide characterization of DcHsp90 gene family in carnation (Dianthus caryophyllus L.) and functional analysis of DcHsp90-6 in heat tolerance

Plant heat shock protein 90 (Hsp90) participates in various physiological processes including protein folding, degradation, and signal transduction. However, the DcHsp90 gene family in carnation (Dianthus caryophyllus L.) has not been systematically analyzed. We thoroughly examined and comprehensively analyzed the carnation DcHsp90 gene family in this study and discovered 9 DcHsp90 genes. Based on the phylogenetic examination, DcHsp90 proteins may be divided into two groups. DcHsp90 structural features were similar but varied between groups. Promoter analysis revealed the presence of many cis-acting elements, most of which were connected to growth and development, hormones, and stress. DcHsp90 genes may play distinct functions in heat stress response, according to gene expression analyses. The DcHsp90-6 was isolated, and its role in the reaction to heat stress was studied. Thermotolerance and superoxide dismutase activity in transgenic seedlings were enhanced by Arabidopsis overexpression of DcHsp90-6. After heat stress, transgenic plants' electrolyte leakage and malondialdehyde levels were much lower than wild-type plants. Furthermore, overexpression of DcHsp90-6 altered the expressions of stress-responsive genes such as AtHsp101, AtHsp90, AtGolS1, AtRS4/5, and AtHsfB1. This study provides comprehensive information on the DcHsp90 gene family and suggests that overexpressed DcHsp90-6 positively regulates thermotolerance highlighting the adaptation mechanism of carnation under heat stress.

Exogenous melatonin ameliorates heat damages by regulating growth, photosynthetic efficiency and leaf ultrastructure of carnation

Carnation (Dianthus caryophyllus L.) is a floral crop that is highly valuable commercially. However, high temperatures adversely affect its growth and the quality of its cut flowers. Melatonin (MT) is a indole substance that can mitigate plant damage under heat stress. In this study, the leaves of carnation seedlings were sprayed with different concentrations of MT before exposure to high temperature. The indices of growth, physiological and chlorophyll fluorescence were measured and analyzed by the membership function method. The results showed that treatment with 100 μM MT was the most effective at ameliorating damage on carnation. We then analyzed the effects of 100 μM MT pretreatment on carnation at different time points of heat stress and found that this concentration of MT ameliorated the damage caused by heat stress, increased the content of photosynthetic pigments, enhanced the performance of photosystem II and improved photosynthesis. In addition, MT also reduced cell damage and lipid peroxidation, increased the activities of antioxidant enzymes and regulated the accumulation of osmotic substances in carnation. Moreover, MT increased the fresh/dry weight of stems and roots, promoted the opening of stomata, and protected the integrity of chloroplast structure of carnation. Compared with heat stress, pre-spraying with MT significantly down-regulated the transcription of a chlorophyll degradation gene and up-regulated the transcription of stress-related genes. Overall, this study provides a theoretical foundation for the mitigation of the adverse effects of exogenous MT under heat stress and proposes beneficial implications for the management of other plants subjected to global warming.

Genome-wide analysis of HSP20 gene family and expression patterns under heat stress in cucumber (Cucumis sativus L.)

Cucumber is an important vegetable in China, and its yield and cultivation area are among the largest in the world. Excessive temperatures lead to high-temperature disorder in cucumber. Heat shock protein 20 (HSP20), an essential protein in the process of plant growth and development, is a universal protective protein with stress resistance. HSP20 plays crucial roles in plants under stress. In this study, we characterized the HSP20 gene family in cucumber by studying chromosome location, gene duplication, phylogenetic relationships, gene structure, conserved motifs, protein-protein interaction (PPI) network, and cis-regulatory elements. A total of 30 CsHSP20 genes were identified, distributed across 6 chromosomes, and classified into 11 distinct subgroups based on conserved motif composition, gene structure analyses, and phylogenetic relationships. According to the synteny analysis, cucumber had a closer relationship with Arabidopsis and soybean than with rice and maize. Collinearity analysis revealed that gene duplication, including tandem and segmental duplication, occurred as a result of positive selection and purifying selection. Promoter analysis showed that the putative promoters of CsHSP20 genes contained growth, stress, and hormone cis-elements, which were combined with protein-protein interaction networks to reveal their potential function mechanism. We further analyzed the gene expression of CsHSP20 genes under high stress and found that the majority of the CsHSP20 genes were upregulated, suggesting that these genes played a positive role in the heat stress-mediated pathway at the seedling stage. These results provide comprehensive information on the CsHSP20 gene family in cucumber and lay a solid foundation for elucidating the biological functions of CsHSP20. This study also provides valuable information on the regulation mechanism of the CsHSP20 gene family in the high-temperature resistance of cucumber.