Phylogenetic and expression dynamics of tomato ClpB/Hsp100 gene under heat stress.

Heat shock proteins (Hsps) are stress-responsive molecular chaperones, which uphold proper protein folding in response to external and internal stresses. The Hsp100 gene family plays a substantial role in thermos-tolerance of plants. This study investigated evolutionary relationship and expression of ClpB/Hsp100 gene family in tomato under heat stress. Six SlHsp100 genes were identified using bioinformatics tools. In silico sub-cellular localization indicated that of these 6 ClpB/Hsp100 members, 4 are found in chloroplast, 1 in mitochondria and 1 in the cytoplasm. For evolutionary study, 36 SlHsp100 genes were included in the phylogenetic tree showing a hierarchical clustering shared by the members of the kingdoms Plantae, Archaea, Chromista, Fungi and Bacteria. A total 4 pairs of orthologous and 5 pairs of paralogous genes were identified. Functional divergence between different Hsp100 clusters showed considerable functional homology. Thermo-tolerance measured in terms of cell viability, cell membrane stability and pollen viability indicated that it was paralleled by thermal resistance of Hsps. Reverse transcriptase polymerase chain reaction was used to analyze gene expression in leaves of five-week-old tomato seedlings following exposure to heat stress (45°C) and control (25°C). Chloroplastic LeHSP110/ClpB gene was upregulated in all tomato genotypes after exposure to heat stress highlighting the crucial role of this gene family in acquired thermo-tolerance.

Phenotyping for drought resistance in bread wheat using physiological and biochemical traits.

Drought is one of the most prominent limiting factors that negatively affect crop productivity by manipulating its physiological pathway. One hundred twenty diverse bread wheat genotypes were used in a pot experiment to explore the relationship among their fifteen physio-biochemical traits (PBT) by using multivariate analysis, heatmapping and stress tolerance index (STI) for grain yield as a marker trait to identify high yielding genotype with maximum stress tolerance capability. Increased proline and sugar accumulation were observed from control to moisture deficient environments by 159% and 122%, respectively. Moreover, leaf membrane stability index (LMSI), leaf relative water content (LRWC), relative dry weight (RDW), chlorophyll content, leaf surface area (LSA), Leaf succulence (LS), canopy temperature depression (CTD), relative excised leaf water loss (RELWL) and leaf osmotic potential (LOP) showed significantly decreasing trend in drought stress treatment as compared to well-watered plants by -21%, -21%, -34%, -22%, -38%, -37%, -46%, -18% and -35% respectively. Additionally, principal component analysis and genotype by trait biplot analysis showed that initial 7 principal components (PC1 to PC7) represented 77.27% and 79.02% of total cumulative variation under control and drought stress respectively. Genotypic-Phenotypic correlation revealed that most of the attributes were higher in case of genotypic correlation component (rg) as compared to the phenotypic correlation component (rp) indicating more genetic association between traits. The darker and lighter colour scale produced by heatmap exhibited contrasting nature of genotypes, as positive side with higher values represented drought resistance while values on the negative side with lower values showed susceptible performance of genotypes. Our results concluded that the studied PBT associated with STI for grain yield are the main factors which may contribute in improved productivity of wheat crop and if these traits show appropriate performance under stress condition the crop will show the more productive returns under changing climate.