Overexpression of Sugarcane ScDIR Genes Enhances Drought Tolerance in Nicotiana benthamiana

Comparative transcriptomic analyses of two sugarcane Saccharum L. cultivars differing in drought tolerance

Sugarcane (Saccharum spp.) is an important cash crop, and drought is an important factors limiting its yield. To study the drought resistance mechanism of sugarcane, the transcriptomes of two sugarcane varieties with different levels of drought resistance were compared under different water shortage levels. The results showed that the transcriptomes of the two varieties were significantly different. The differentially expressed genes were enriched in starch and sucrose metabolism, linoleic acid metabolism, glycolysis/gluconeogenesis, and glyoxylate and dicarboxylate metabolic pathways. Unique trend genes of the variety with strong drought resistance (F172) were significantly enriched in photosynthesis, mitogen-activated protein kinases signaling pathway, biosynthesis of various plant secondary metabolites, and cyanoamino acid metabolism pathways. Weighted correlation network analysis indicated that the blue4 and plum1 modules correlated with drought conditions, whereas the tan and salmon4 modules correlated with variety. The unique trend genes expressed in F172 and mapped to the blue4 module were enriched in photosynthesis, purine metabolism, starch and sucrose metabolism, beta-alanine metabolism, photosynthesis-antenna proteins, and plant hormone signal transduction pathways. The expression of genes involved in the photosynthesis-antenna protein and photosynthesis pathways decreased in response to water deficit, indicating that reducing photosynthesis might be a means for sugarcane to respond to drought stress. The results of this study provide insights into drought resistance mechanisms in plants, and the related genes and metabolic pathways identified may be helpful for sugarcane breeding in the future.

Genome-wide identification, characterization, evolution and expression analysis of the DIR gene family in potato (Solanum tuberosum)

The dirigent (DIR) gene is a key player in environmental stress response and has been identified in many multidimensional tube plant species. However, there are few studies on the StDIR gene in potato. In this study, we used genome-wide identification to identify 31 StDIR genes in potato. Among the 12 potato chromosomes, the StDIR gene was distributed on 11 chromosomes, among which the third chromosome did not have a family member, while the tenth chromosome had the most members with 11 members. 22 of the 31 StDIRs had a classical DIR gene structure, with one exon and no intron. The conserved DIR domain accounts for most of the proteins in the 27 StDIRs. The structure of the StDIR gene was analyzed and ten different motifs were detected. The StDIR gene was divided into three groups according to its phylogenetic relationship, and 22 duplicate genes were identified. In addition, four kinds of cis-acting elements were detected in all 31 StDIR promoter regions, most of which were associated with biotic and abiotic stress. The findings demonstrated that the StDIR gene exhibited specific responses to cold stress, salt stress, ABA, and drought stress. This study provides new candidate genes for improving potato's resistance to stress.

Drought and salinity stresses induced physio-biochemical changes in sugarcane: an overview of tolerance mechanism and mitigating approaches

Sugarcane productivity is being hampered globally under changing environmental scenarios like drought and salinity. The highly complex nature of the plant responses against these stresses is determined by a variety of factors such as genotype, developmental phase of the plant, progression rate and stress, intensity, and duration. These factors influence plant responses and can determine whether mitigation approaches associated with acclimation are implemented. In this review, we attempt to summarize the effects of drought and salinity on sugarcane growth, specifically on the plant's responses at various levels, viz., physiological, biochemical, and metabolic responses, to these stresses. Furthermore, mitigation strategies for dealing with these stresses have been discussed. Despite sugarcane's complex genomes, conventional breeding approaches can be utilized in conjunction with molecular breeding and omics technologies to develop drought- and salinity-tolerant cultivars. The significant role of plant growth-promoting bacteria in sustaining sugarcane productivity under drought and salinity cannot be overlooked.

Overexpression of NtGCN2 improves drought tolerance in tobacco by regulating proline accumulation, ROS scavenging ability, and stomatal closure

Drought stress is a severe threat to plants. Genes that respond to drought stress are essential for plant growth and development. General control nonderepressible 2 (GCN2) encodes a protein kinase that responds to various biotic and abiotic stresses. However, the mechanism of GCN2 in plant drought tolerance remains unclear. In the present study, the promoters of NtGCN2 from Nicotiana tabacum K326, which contained a drought-responsive Cis-acting element MYB that can be activated by drought stress, were cloned. Furthermore, the drought tolerance function of NtGCN2 was investigated using NtGCN2-overexpressed transgenic tobacco plants. NtGCN2-overexpressed transgenic plants were more tolerant to drought stress than wild-type (WT) plants. The transgenic tobacco plants exhibited higher proline and abscisic acid (ABA) contents, antioxidant enzyme activities, leaf relative water content, and expression levels of genes encoding key antioxidant enzymes and proline synthase, but lower levels of malondialdehyde and reactive oxygen species, and reduced stomatal apertures, stomatal densities, and stomatal opening rates compared to WT plants under drought stress. These results indicated that overexpression of NtGCN2 conferred drought tolerance in transgenic tobacco plants. RNA-seq analysis showed that overexpression of NtGCN2 responded to drought stress by regulating the expression of genes related to proline synthesis and catabolism, abscisic acid synthesis and catabolism, antioxidant enzymes, and ion channels in guard cells. These results showed that NtGCN2 might regulate drought tolerance by regulating proline accumulation, reactive oxygen species (ROS) scavenging, and stomatal closure in tobacco and may have the potential for application in the genetic modification of crop drought tolerance.