Search

The small heat shock proteins (sHsps/Hsp20s) are the molecular chaperones that maintain proper folding, trafficking and disaggregation of proteins under diverse abiotic stress conditions. In the present investigation, a genome-wide scan revealed the presence of a total of 47 sHsps in Sorghum bicolor (SbsHsps), distributed across 10 subfamilies, the major subfamily being P (plastid) group with 17 genes. Chromosomes 1 and 3 appear as the hot spot regions for SbsHsps, and majority of them were found acidic, hydrophilic, unstable and intron less. Interestingly, promoter analysis indicated that they are associated with both biotic and abiotic stresses, as well as plant development. Sorghum sHsps exhibited 15 paralogous and 20 orthologous duplications. Expression analysis of 15 genes selected from different subfamilies showed high transcript levels in roots and leaves implying that they are likely to participate in the developmental processes. SbsHsp genes were highly induced by diverse abiotic stresses inferring their critical role in mediating the environmental stress responses. Gene expression data revealed that SbsHsp-02 is a candidate gene expressed in all the tissues under varied stress conditions tested. Our results contribute to the understanding of the complexity of SbsHsp genes and help to analyse them further for functional validation.

Lysine (Lys) is indispensable nutritionally, and its levels in plants are modulated by both transcriptional and post-transcriptional control during plant ontogeny. Animal glutamate receptor homologs have been detected in plants, which may participate in several plant processes through the Lys catabolic products. Interestingly, a connection between Lys and serotonin metabolism has been established recently in rice. 2-Aminoadipate, a catabolic product of Lys appears to play a critical role between serotonin accumulation and the color of rice endosperm/grain. It has also been shown that expression of some lysine-methylated proteins and genes encoding lysine-methyltransferases (KMTs) are regulated by cadmium even as it is known that Lys biosynthesis and its degradation are modulated by novel mechanisms. Three complex pathways co-exist in plants for serine (Ser) biosynthesis, and the relative preponderance of each pathway in relation to plant development or abiotic stress tolerance are being unfolded slowly. But the phosphorylated pathway of L-Ser biosynthesis (PPSB) appears to play critical roles and is essential in plant metabolism and development. Ser, which participates indirectly in purine and pyrimidine biosynthesis and plays a pivotal role in plant metabolism and signaling. Also, L-Ser has been implicated in plant responses to both biotic and abiotic stresses. A large body of information implicates Lys-rich and serine/arginine-rich (SR) proteins in a very wide array of abiotic stresses. Interestingly, a link exists between Lys-rich K-segment and stress tolerance levels. It is of interest to note that abiotic stresses largely influence the expression patterns of SR proteins and also the alternative splicing (AS) patterns. We have checked if any lncRNAs form a cohort of differentially expressed genes from the publicly available PPSB, sequence read archives of NCBI GenBank. Finally, we discuss the link between Lys and Ser synthesis, catabolism, Lys-proteins, and SR proteins during plant development and their myriad roles in response to abiotic stresses.

The Cucurbita genus, often called as cucurbits, include several economically important fruits and vegetable crops like cucumber, gourds, squash, watermelon, pumpkin, and melon. Several of the species including Cucurbita pepo and C. maxima have nutritional value and are utilized in folk medicine for treating gastrointestinal diseases and intestinal parasites. Such an activity is attributed to the presence of fatty acids, glycosides, resins, sterols, carotenoids, phenols, tocopherols, saponins, steroids, and terpenoids such as cucurbitacins. Squash and pumpkin are the major members of Cucurbitaceae family used as food and animal feed. The two major pumpkin varieties C. pepo and C. maxima are considered as highly polymorphic with manifold nutritional, including food preservative abilities and medicinal activities. Development of transgenic pepo for tolerance to various biotic and abiotic stresses coupled with nutritional value is the need of the hour. Very few reports are available on transgenic production of pepo. The present review summarizes the regeneration and transformation protocols for developing transgenic C. pepo and C. maxima and future prospects.

Tomato (Lycopersicon esculentum Mill.) is the second most important vegetable crop of the world. It is rich in nutrition with zero cholesterol, but highly sensitive to abiotic stresses, especially salt, drought, and high temperatures. Development of transgenic tomatoes that are climate resilient coupled with high nutritional value and improved shelf-life of fruit is the need of the hour. Utilization of conventional plant breeding methods and genetic engineering technologies must therefore be vital to achieve these goals. Tomatoes overexpressing transgenes and transcription factors conferred tolerance against different abiotic stresses with increased fruit production in comparison with wild-type (WT) plants. Similarly, delayed fruit ripening and nutritional quality of the fruit have been achieved in tomato. The present review describes the current status of the development of transgenic tomatoes that are tolerant to diverse abiotic stresses alongside delayed fruit ripening and other quality attributes and projects the potential areas for future research.

The DnaJ/Hsp40s, are important components in the chaperone machine, and play pivotal roles in plant growth, development and stress tolerance. Sorghum, the semi-arid crop, is the drought resilient, model C4 crop. However, no reports of DnaJs have been available. Genome-wide analysis of Sorghum bicolor revealed 113 DnaJ/Hsp40 genes, classified into four groups; 8 genes in SbDnaJ-A class, 10 in SbDnaJ-B, 82 in SbDnaJ-C and 13 in SbDnaJ-D distributed unevenly on all the 10 chromosomes. Chromosomes 1 and 3 were found hot spots with 22 and 20 genes respectively. All genes displayed large number of introns, with an exception of 11 of the SbDnaJ-C which is devoid of introns. Out of 36 paralogous duplications, 7 tandem and 29 segmental duplications were noticed, indicating the major role of segmental duplications in the expansion. Analysis of digital data revealed tissue and stage-specific expressions. Transcriptional profiling of 12 selected genes representing all 4 classes revealed highly significant expression in leaf followed by root tissues. No expression was noticed in stems with an exception of SbDnaJ-C76. The SbDnaJ-A1, D1, and C subgroup genes displayed upregulation in roots, stems and leaves under cold, inferring the involvement of Hsp40s for cellular protection during cold stress. The results demonstrate that C76 and D1 are the candidate genes associated with multiple abiotic stresses. Present research furnishes valuable information about the role of sorghum DnaJs in abiotic stress response and establishes a foundation for understanding the molecular mechanisms associated with plant development and stress tolerance.

Many of the drugs that are sold in the market today are mostly the synthetic modifications of the naturally available plant products. Many have been resorting to natural sources of remedies since they have less side effects. Since a large number of secondary plant products have commercial importance, there is a renewed interest in the possibility of altering the production of bioactive compounds using in vitro techniques. Plants produce low amounts of secondary plant products or bioactive compounds, and hence in vitro grown callus, suspensions, and morphogenic cultures are being exploited for enhanced production. Detection and increased production of secondary metabolites have been reported in diverse medicinal plants. The present review is aimed to cover recent advances for the production of some important plant pharmaceuticals from selected plant species.

Morphogenic cultures of Gloriosa superba were initiated on Murashige and Skoog’s medium fortified with 2 mg L−1 2,4-dichlorophenoxyacetic acid (2,4-D), 0.5 mg L−1 naphthaleneacetic acid (NAA), 4% sucrose and 0.1% activated charcoal. To enhance the content of the alkaloid colchicine, morphogenic cultures were treated with different concentrations of abiotic elicitors like signalling compounds, metals, biotic elicitors, precursors and a combination of elicitors. Signalling molecules like acetyl salicylic acid (ASA) and sodium nitroprusside improved the production of colchicine. Abiotic elicitors have markedly (p ≤ 0.05 or ≤ 0.01) enhanced the colchicine content either at lower or higher concentrations. Among the metals, the highest amount of 11.67 mg of colchicine g−1 dry wt was noticed at 60 mM rubidium chloride, followed by 60 mM NaCl (11.18 mg g−1). Contrarily, in the presence of biotic elicitors such as Fusarium oxysporum, Alternaria solani, and Saccharomyces cerevisiae, colchicine content ranged only between 2 and 5.32 mg g−1, but Bacillus subtilis repressed it. Among the aromatic amino acids, phenylalanine at 500 mg L−1 influenced the highest accumulation of 19.48 mg g−1 dry tissue, followed by tryptophan (12.47 mg g−1), and tyrosine (9.87 mg g−1), a direct precursor of colchicine biosynthesis, while intact tubers and leaves contained 4.65 and 4.16 mg of colchicine g−1 dry tissue respectively. A combination of 10 µM AlCl3 and 50 µM salicylic acid (SA) registered 17.34 mg g−1 followed by 16.24 mg g−1 tissue in presence of 1 µM HgCl2 and 50 µM SA. The results suggest that the elicitor-stimulated colchicine accumulation was a stress response and can be exploited further for commercial production.

Members of the plant Heme Activator Protein (HAP) or NUCLEAR FACTOR Y (NF-Y) are trimeric transcription factor complexes composed of the NF-YA, NF-YB and NF-YC subfamilies. They bind to the CCAAT box in the promoter regions of the target genes and regulate gene expressions. Plant NF-Ys were reported to be involved in adaptation to several abiotic stresses as well as in development. In silico analysis of Sorghum bicolor genome resulted in the identification of a total of 42 NF-Y genes, among which 8 code for the SbNF-YA, 19 for SbNF-YB and 15 for the SbNF-YC subunits. Analysis was also performed to characterize gene structures, chromosomal distribution, duplication status, protein subcellular localizations, conserved motifs, ancestral protein sequences, miRNAs and phylogenetic tree construction. Phylogenetic relationships and ortholog predictions displayed that sorghum has additional NF-YB genes with unknown functions in comparison with Arabidopsis. Analysis of promoters revealed that they harbour many stress-related cis-elements like ABRE and HSE, but surprisingly, DRE and MYB elements were not detected in any of the subfamilies. SbNF-YA1, 2, and 6 were found upregulated under 200 mM salt and 200 mM mannitol stresses. While NF-YA7 appeared associated with high temperature (40°C) stress, NF-YA8 was triggered by both cold (4°C) and high temperature stresses. Among NF-YB genes, 7, 12, 15, and 16 were induced under multiple stress conditions such as salt, mannitol, ABA, cold and high temperatures. Likewise, NF-YC 6, 11, 12, 14, and 15 were enhanced significantly in a tissue specific manner under multiple abiotic stress conditions. Majority of the mannitol (drought)-inducible genes were also induced by salt, high temperature stresses and ABA. Few of the high temperature stress-induced genes are also induced by cold stress (NF-YA2, 4, 6, 8, NF-YB2, 7, 10, 11, 12, 14, 16, 17, NF-YC4, 6, 12, and 13) thus suggesting a cross talk among them. This work paves the way for investigating the roles of diverse sorghum NF-Y proteins during abiotic stress responses and provides an insight into the evolution of diverse NF-Y members.

Na+ transporters play an important role during salt stress and development. The present study is aimed at genome-wide identification, in silico analysis of sodium-proton antiporter (NHX) and sodium-proton exchanger (NHE)-type transporters in Sorghum bicolor and their expression patterns under varied abiotic stress conditions. In Sorghum, seven NHX and nine NHE homologs were identified. Amiloride (a known inhibitor of Na+/H+ exchanger activity) binding motif was noticed in both types of the transporters. Chromosome 2 was found to be a hotspot region with five sodium transporters. Phylogenetic analysis inferred six ortholog and three paralog groups. To gain an insight into functional divergence of SbNHX/NHE transporters, real-time gene expression was performed under salt, drought, heat, and cold stresses in embryo, root, stem, and leaf tissues. Expression patterns revealed that both SbNHXs and SbNHEs are responsive either to single or multiple abiotic stresses. The predicted protein–protein interaction networks revealed that only SbNHX7 is involved in the calcineurin B-like proteins (CBL)- CBL interacting protein kinases (CIPK) pathway. The study provides insights into the functional divergence of SbNHX/NHE transporter genes with tissue specific expressions in Sorghum under different abiotic stress conditions.

Nearly 1200 million hectares of land is affected by salinity throughout the world, and it is increasing year after year. It is one of the major causes that threaten our crop productivity at a time when we need to meet our growing food demands with limited land and freshwater resources. This leaves us but to understand the complex salinity tolerance mechanisms adapted by halophytic species especially their stomatal conductance (gs), epidermal salt bladders, and water use efficiency (WUE) and to utilize the candidate genes associated with them in crop plants for better tolerance and crop productivity.