Whole plant response of Pongamia pinnata to drought stress tolerance revealed by morpho-physiological, biochemical and transcriptome analysis.

BACKGROUND: Pongamia is considered an important biofuel species worldwide. Drought stress in the early growth stages of Pongamia influences negatively on the germination and seedling development. Due to lack of cultivar stability under drought stress conditions, establishment of successful plantation in drought hit areas becomes a major problem. To address this issue, drought stress response of four Pongamia genotypes was studied at morphological, physio-chemical and transcriptome levels. METHODS AND RESULTS: Drought stress was levied by limiting water for 15 days on three months old seedlings of four genotypes. A significant effect of water stress was observed on the traits considered. The genotype NRCP25 exhibited superior morpho-physiological, biochemical drought responses. Also, the genotype had higher root length, photosynthetic pigments, higher antioxidant enzymes and solute accumulation compared to other genotypes. In addition, transcript profiling of selected drought responsive candidate genes such as trehalose phosphate synthase 1 (TPS1), abscisic acid responsive elements-binding protein 2 (ABF2-2), heat shock protein 17 (HSP 17 kDa), tonoplast intrinsic protein 1 (TIP 1-2), zinc finger homeodomain protein 2 (ZFP 2), and xyloglucan endotransglucolase 13 (XET 13) showed only up-regulation in NRCP25. Further, the transcriptome responses are in line with key physio-chemical responses exhibited by NRCP25 for drought tolerance. CONCLUSIONS: As of now, there are no systematic studies on Pongamia drought stress tolerance; therefore this study offers a comprehensive understanding of whole plant drought stress responsiveness of Pongamia. Moreover, the results support important putative trait indices with potential candidate genes for drought tolerance improvement of Pongamia.

Differential responses of sorghum genotypes to drought stress revealed by physio-chemical and transcriptional analysis.

Sorghum is an essential food crop for millions of people in the semi-arid regions of the world, where its production is severely limited by drought stress. Drought in the early stages of crop growth and development irreversibly interferes, which leads to poor yield. The effect of drought stress in sorghum was studied at physiological, biochemical, and molecular levels in a set of two genotypes differing in their tolerance to drought. Drought stress was imposed by restraining water for 10 days on 25 days old seedlings. A significant influence of water stress was observed on the considered morpho-physiological and biochemical traits. The genotype DRT1019 exhibited physiological and biochemical indicators of drought avoidance through delayed leaf rolling, osmotic adjustment, ideal gas-exchange system, solute accumulation, an increased level of enzyme synthesis and root trait expression as compared to the ICSV95022 genotype. Furthermore, differences in the metabolite changes viz. total carbohydrate, total amides, and lipids were found between the two genotypes under drought stress. In addition, transcript profiling of potential candidate drought genes such as SbTIP3-1, SbDHN1, SbTPS, and SbDREB1A revealed up-regulation in DRT1019, which corresponded with other important physiological and biochemical parameters exhibited in the genotype. In conclusion, this study provides an improved understanding of whole plant response to drought stress in sorghum. Additionally, our results provide promising candidate genes for drought tolerance in sorghum that can be used as potential markers for drought tolerance breeding programs.

Comparative analysis of drought-responsive transcriptomes of sugarcane genotypes with differential tolerance to drought.

Water stress causes considerable yield losses in sugarcane. To investigate differentially expressed genes under water stress, two sugarcane genotypes were subjected to three water-deficit levels (mild, moderate, and severe) and subsequent recovery and leaf transcriptome was generated using Illumina NextSeq sequencing. Among the differentially expressed genes, the tolerant genotype Co 06022 generated 2970 unigenes (p ≤ 0.05, functionally known, non-redundant DEGs) at 2-day stress, and there was a progressive decrease in the expressed genes as the stress period increased with 2109 unigenes at 6-day stress and 2307 unigenes at 10-day stress. There was considerable reduction at recovery with 1334 unigenes expressed at 10 days after recovery. However, in the susceptible genotype Co 8021, the number of unigenes expressed at 2 days was lower (2025) than the tolerant genotype and a further reduction was seen at 6-day stress (1552). During recovery, more differentially expressed genes were observed in the susceptible cultivar indicating that the cultivar has to activate more functions/processes to recover from the damage caused by stress. Comparison of DEGs between all stages of stress and recovery in both genotypes revealed that, the commonly up- and down-regulated genes across different stages were approximately double in the tolerant genotype. The most enriched gene ontology classes were heme binding, peroxidase activity and metal ion binding in the biological process and response to oxidative stress, hydrogen peroxide catabolic process and response to stress in the molecular function category. The cellular component was enriched with DEGs involved in extracellular region followed by integral component of membrane. The KEGG pathway analysis revealed important metabolic activities and functionally important genes involved in mitigating water-deficit stress in both the varieties. In addition, several unannotated genes in important pathways were detected and together may provide novel insights into water-deficit tolerance mechanisms in sugarcane. The reliability of the observed expression patterns was confirmed by qRT-PCR. The results of this study will help to identify useful genes for improving drought tolerance in sugarcane.

Comparison of modified chin lift technique with EC technique for mask ventilation in adult apneic patients.

BACKGROUND: Mask ventilation (MV) is an essential basic life support skill. We used chin lift maneuver for MV and named as modified chin lift technique (MCL). EC technique is most common technique used for MV. AIMS: The aim of this study is to compare the efficacy of both techniques for MV in term of expired tidal volume (TV). Secondarily, we also assessed the effect of experience on the performance of these both techniques. SETTINGS AND DESIGN: The study area was operation theater of our hospital. This was a prospective, randomized, crossover study. METHODS: A total 108 adults undergoing elective surgery under general anesthesia were recruited. In all patients, operators (novice/anesthesiologist) randomly performed both techniques either to start with EC or MCL technique. Expired TV was measured for one minute for each technique. STATISTICAL ANALYSIS: Paired t-test was used to compare TV. RESULTS AND CONCLUSION: The mean TV was significantly higher in MCL group than EC group (528.08 [104.96] ml vs. 483.39 [103] ml; P < 0.001). The novice (521.89 [117.9] ml vs. 478.70 [130.29] ml; P < 0.001) as well as anesthesiologists (534.27 [110.85] ml vs. 488.08 [111.6] ml; P < 0.001) was able to generate significantly more TV with MCL technique than EC technique. The TV did not differ significantly between novice and anesthesiologist for EC technique (P = 0.474) or MCL technique (P = 0.187). Novices as well as anesthesiologist felt MCL technique more satisfactory (70%). CLINICAL TRIAL REGISTRATION: CTRI/2016/04/006874.

Expression profiling of sucrose metabolizing genes in Saccharum, Sorghum and their hybrids.

Sucrose phosphate synthase (SPS; EC 2.4.1.14), sucrose synthase (SuSy; EC 2.4.1.13) and soluble acid invertase (SAI; EC 3.2.1.26) are key enzymes that regulate sucrose fluxes in sink tissues for sucrose accumulation in sugarcane and sorghum. In this study, the expression profiling of sucrose-related genes, i.e. SPS, SuSy and SAI in two sets of hybrids viz., one from a Sorghum × Saccharum cross and the other from a Saccharum × Sorghum cross, high- and low-sucrose varieties, sweet and grain sorghum lines was carried out using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) at monthly intervals. The results indicated differential expression of the three genes in high- and low-sucrose forms. Expression of SPS and SuSy genes was high in high-sucrose varieties, Saccharum × Sorghum hybrids and sweet sorghum and lower in low-sucrose varieties, Sorghum × Saccharum hybrids and grain sorghum. SAI showed a lower expression in high-sucrose varieties, Saccharum × Sorghum hybrids and sweet sorghum and higher expression in low-sucrose varieties, Sorghum × Saccharum hybrids and the grain sorghum. This study describes the positive association of SPS and SuSy and negative association of SAI on sucrose accumulation. This is the first report of differential expression profiling of SPS, SuSy and SAI in intergeneric hybrids involving sugarcane and sorghum, which opens the possibility for production of novel hybrids with improved sucrose content and with early maturity.

Differential regulation of defense-related gene expression in response to red rot pathogen Colletotrichum falcatum infection in sugarcane.

Red rot is a serious disease of sugarcane caused by the fungus Colletotrichum falcatum imposing a considerable economic loss annually in all sugarcane-producing countries. In this study, we analyzed the early resistance response of sugarcane to red rot fungus by comparing the differences between control and inoculated stalk tissues. Differential display reverse transcription polymerase chain reaction (DD-RT-PCR) was employed to identify altered expression of genes in disease-resistant cv Co 93009, in response to pathogen infection. DD-RT-PCR identified 300 differentially expressed transcripts of which 112 were selected for further analysis. Cloning and sequence analysis of the isolated cDNA fragments resulted in functional categorization of these clones into five categories, of which the defense/stress/signaling group was the largest, with clones homologous to genes known to be actively involved in various pathogenesis-related functions in plant species. This group showed overexpression of several transcripts related to ethylene-mediated and jasmonic acid pathway of plant defense mechanisms. Of the 112 expressed sequence tags, validation of expression was carried out for five important genes whose role in plant defense mechanisms is well established. This is the first report of Colletotrichum-mediated gene regulation in sugarcane which has provided a set of candidate genes for detailed molecular dissection of signaling and defense responses in tropical sugarcane during the onset of red rot resistance.