Comprehensive Analysis of GH3 Gene Family in Potato and Functional Characterization of StGH3.3 under Drought Stress.

As an important hormone response gene, Gretchen Hagen 3 (GH3) maintains hormonal homeostasis by conjugating excess auxin with amino acids during plant stress-related signaling pathways. GH3 genes have been characterized in many plant species, but they are rarely reported in potato. Here, 19 StGH3 genes were isolated and characterized. Phylogenetic analysis indicated that StGH3s were divided into two categories (group I and group III). Analyses of gene structure and motif composition showed that the members of a specific StGH3 subfamily are relatively conserved. Collinearity analysis of StGH3 genes in potato and other plants laid a foundation for further exploring the evolutionary characteristics of the StGH3 genes. Promoter analysis showed that most StGH3 promoters contained hormone and abiotic stress response elements. Multiple transcriptome studies indicated that some StGH3 genes were responsive to ABA, water deficits, and salt treatments. Moreover, qRT-PCR analysis indicated that StGH3 genes could be induced by phytohormones (ABA, SA, and MeJA) and abiotic stresses (water deficit, high salt, and low temperature), although with different patterns. Furthermore, transgenic tobacco with transient overexpression of the StGH3.3 gene showed positive regulation in response to water deficits by increasing proline accumulation and reducing the leaf water loss rate. These results suggested that StGH3 genes may be involved in the response to abiotic stress through hormonal signal pathways. Overall, this study provides useful insights into the evolution and function of StGH3s and lays a foundation for further study on the molecular mechanisms of StGH3s in the regulation of potato drought resistance.

Foliar Application of Chelated Sugar Alcohol Calcium Improves Photosynthesis and Tuber Quality under Drought Stress in Potatoes (Solanum tuberosum L.).

Drought stress is a major threat to sustainable crop production worldwide. Despite the positive role of calcium (Ca2+) in improving plant drought tolerance in different crops, little attention has been paid to its role in mitigating drought stress in potatoes. In the present study, we studied the effect of foliar chelated sugar alcohol calcium treatments on two potato cultivars with different drought responses applied 15 and 30 days after limiting soil moisture. The results showed that the foliar application of calcium treatments alleviated the SPAD chlorophyll loss of the drought-sensitive cultivar 'Atlantic' (Atl) and reduced the inhibition of photosynthetic parameters, leaf anatomy deformation, and MDA and H2O2 content of both cultivars under drought stress. The Ca2+ treatments changed the expression of several Calcium-Dependent Protein Kinase (StCDPK) genes involved in calcium sensing and signaling and significantly increased antioxidant enzyme activities, average tuber weight per plant, and tuber quality of both cultivars. We conclude that calcium spray treatments improved the drought tolerance of both potato cultivars and were especially effective for the drought-sensitive cultivar. The present work suggests that the foliar application of calcium is a promising strategy to improve commercial potato yields and the economic efficiency of potato production under drought stress conditions.

Comparative Transcriptome Profiling Reveals Potential Candidate Genes, Transcription Factors, and Biosynthetic Pathways for Phosphite Response in Potato (Solanum tuberosum L.).

The study was conducted with C31 and C80 genotypes of the potato (Solanum tuberosum L.), which are tolerant and susceptible to phosphite (Phi, H2PO3), respectively. To decipher the molecular mechanisms underlying tolerance and susceptibility to Phi in the potato, RNA sequencing was used to study the global transcriptional patterns of the two genotypes. Media were prepared with 0.25 and 0.50 mM Phi, No-phosphorus (P), and 1.25 mM (phosphate, Pi as control). The values of fragments per kilobase of exon per million mapped fragments of the samples were also subjected to a principal component analysis, grouping the biological replicates of each sample. Using stringent criteria, a minimum of 819 differential (DEGs) were detected in both C80-Phi-0.25_vs_C80-Phi-0.50 (comprising 517 upregulated and 302 downregulated) and C80-Phi-0.50_vs_C80-Phi-0.25 (comprising 302 upregulated and 517 downregulated) and a maximum of 5214 DEGs in both C31-Con_vs_C31-Phi-0.25 (comprising 1947 upregulated and 3267 downregulated) and C31-Phi-0.25_vs_C31-Con (comprising 3267 upregulated and 1947 downregulated). DEGs related to the ribosome, plant hormone signal transduction, photosynthesis, and plant-pathogen interaction performed important functions under Phi stress, as shown by the Kyoto Encyclopedia of Genes and Genomes annotation. The expressions of transcription factors increased significantly in C31 compared with C80. For example, the expressions of Soltu.DM.01G047240, Soltu.DM.08G015900, Soltu.DM.06G012130, and Soltu.DM.08G012710 increased under P deficiency conditions (Phi-0.25, Phi-0.50, and No-P) relative to the control (P sufficiency) in C31. This study adds to the growing body of transcriptome data on Phi stress and provides important clues to the Phi tolerance response of the C31 genotype.

Evolution and expression analysis of CDPK genes under drought stress in two varieties of potato.

OBJECTIVES: Calcium-dependent protein kinases (CDPKs) function directly in plant development and stress responses. We used whole genome sequences and mRNA expression data to analyze the phylogenetic relationships, gene structure, collinearity, and differential expression of CDPKs in two differentially drought-tolerant potato varieties. RESULTS: In total, we identified 25 CDPK proteins belonging to four subfamilies. There was a significant collinear relationship among 13 CDPK genes belonging to four segmentally duplicated pairs. Subcellular prediction implied that all StCDPKs were localized at the plasma membrane. Analysis of promoter regions revealed that StCDPKs were photosensitive and responsive to biotic stress, abiotic stress, and hormone stimuli. RNA-seq analysis showed differential expression of StCDPKs among various potato tissues, and qPCR analysis revealed that 20 StCDPKs exhibited differential expression patterns under drought stress between drought-tolerant (QS9) and drought sensitive (Atl) potato varieties. Among these, the most strongly drought-induced genes were respectively StCDPK3 and StCDPK23, highlighting these as attractive candidate genes for further functional analyses of drought-stress responses in potato. CONCLUSIONS: Our results demonstrating the tissue specific and drought stress-responsive StCDPK genes of potato both provide a reference for further research about the functions of CDPK family proteins and should support ongoing efforts for the further genetic improvement of potato.