Sulfur starvation and restoration affect nitrate uptake and assimilation in rapeseed

We analyzed the effect of omission of sulfur (S) from the nutrient solution and then restoration of S-source on the uptake and assimilation of nitrate in rapeseed. Incubation in nutrient solution without S for 1-6 days led to decline in uptake of nitrate, activities, and expression levels of nitrate reductase (NR) and glutamine synthetase (GS). The nitrite reductase (NiR) and glutamate synthase (GOGAT) activities were not considerably affected. There was significant enhancement in nitrate content and decline in sulfate content. Evaluation of amino acid profile under S-starvation conditions showed two- to fourfold enhancement in the contents of arginine, asparagine and O-acetyl-l-serine (OAS), whereas the contents of cysteine and methionine were reduced heavily. When the S-starved plants were subjected to restoration of S for 1, 3, 5, and 7 days, activities and expression levels of NR and GS recovered within the fifth and seventh days of restoration, respectively. Exogenous supply of metabolites (arginine, asparagine, cysteine, glutamine, OAS, and methionine) also affected the uptake and assimilation of nitrate, with a maximum for OAS. These results corroborate the tight interconnection of S-nutrition with nitrate assimilation and that OAS plays a major role in this regulation. The study must be helpful in developing a nutrient-management technology for optimization of crop productivity

Evaluation of Candidate Reference Genes for Gene Expression Normalization in Brassica juncea Using Real Time Quantitative RT-PCR

The real time quantitative reverse transcription PCR (qRT-PCR) is becoming increasingly important to gain insight into function of genes. Given the increased sensitivity, ease and reproducibility of qRT-PCR, the requirement of suitable reference genes for normalization has become important and stringent. It is now known that the expression of internal control genes in living organism vary considerably during developmental stages and under different experimental conditions. For economically important Brassica crops, only a couple of reference genes are reported till date. In this study, expression stability of 12 candidate reference genes including ACT2, ELFA, GAPDH, TUA, UBQ9 (traditional housekeeping genes), ACP, CAC, SNF, TIPS-41, TMD, TSB and ZNF (new candidate reference genes), in a diverse set of 49 tissue samples representing different developmental stages, stress and hormone treated conditions and cultivars of Brassica juncea has been validated. For the normalization of vegetative stages the ELFA, ACT2, CAC and TIPS-41 combination would be appropriate whereas TIPS-41 along with CAC would be suitable for normalization of reproductive stages. A combination of GAPDH, TUA, TIPS-41 and CAC were identified as the most suitable reference genes for total developmental stages. In various stress and hormone treated samples, UBQ9 and TIPS-41 had the most stable expression. Across five cultivars of B. juncea, the expression of CAC and TIPS-41 did not vary significantly and were identified as the most stably expressed reference genes. This study provides comprehensive information that the new reference genes selected herein performed better than the traditional housekeeping genes. The selection of most suitable reference genes depends on the experimental conditions, and is tissue and cultivar-specific. Further, to attain accuracy in the results more than one reference genes are necessary for normalization

Nitrogen stress-induced alterations in the leaf proteome of two wheat varieties grown at different nitrogen levels

Inorganic nitrogen (N) is a key limiting factor of the agricultural productivity. Nitrogen utilization efficiency has significant impact on crop growth and yield as well as on the reduction in production cost. The excessive nitrogen application is accompanied with severe negative impact on environment. Thus to reduce the environmental contamination, improving NUE is need of an hour. In our study we have deployed comparative proteome analysis using 2-DE to investigate the effect of the nitrogen nutrition on differential expression pattern of leaf proteins in low-N sensitive and low-N tolerant wheat (Triticum aestivum L.) varieties. Results showed a comprehensive picture of the post-transcriptional response to different nitrogen regimes administered which would be expected to serve as a basic platform for further characterization of gene function and regulation. We detected proteins related to photosynthesis, glycolysis, nitrogen metabolism, sulphur metabolism and defence. Our results provide new insights towards the altered protein pattern in response to N stress. Through this study we suggest that genes functioning in many physiological events coordinate the response to availability of nitrogen and also for the improvement of NUE of crops

From agronomy to molecular genetics and proteomics in an effort to improve nitrogen use efficiency in crops

Agriculture plays significant role in the sustaining human society among most of the developing countries. The agricultural practices are dependent on the application of the nitrogenous fertilizers. The excessive application of nitrogenous fertilizer contributes enormously to the environmental pollution. So, in today’s scenario there is growing need to reduce N fertilizer applications thereby improving plant’s N-use efficiency (NUE). Initially, various studies have been carried out to improve inputs of N fertilizers interaction with soil, water and air but low efficiency of the plant to make use of available N has initiated biological interferences. In this article, we will be discussing the possible technologies applied towards understanding the genetic control of nitrogen use efficiency and its improvement in crops. The classification/identification of suitable target candidates like phenotypes, genotypes or molecular markers, for the upgrading of NUE poses big confront. Therefore, it is necessary to understand NUE and its importance with respect to economy and environment. Also, to figure out the diverse approaches for progress towards NUE enhancement and possibilities for future development

Physiological and Molecular Analysis of Applied Nitrogen in Rice Genotypes

Ten genotypes of rice (Oryza sativa L.) were grown for 30 d in complete nutrient solution with 1 mmol/L (N-insufficient), 4 mmol/L (N-moderate) and 10 mmol/L (N-high) nitrogen levels, and nitrogen efficiency (NE) was analyzed. Growth performance, measured in terms of fresh weight, dry weight and lengths of root and shoot, was higher in N-efficient than in N-inefficient rice genotypes at low N level. Of these 10 genotypes, Suraksha was identified as the most N-efficient, while Vivek Dhan the most N-inefficient. To find out the physiological basis of this difference, the nitrate uptake rate of root and the activities of nitrate assimilatory enzymes in leaves of N-efficient and N-inefficient rice genotypes were studied. Uptake experiments revealed the presence of two separate nitrate transporter systems mediating high- and low-affinity nitrate uptake. Interestingly, the nitrate uptake by the roots of Suraksha is mediated by both high- and low-affinity nitrate transporter systems, while that of Vivek Dhan by only low-affinity nitrate transporter system. Study of the activities and expression levels of nitrate assimilatory enzymes in N-efficient and N-inefficient rice genotypes showed that nitrate reductase (NR) and glutamine synthetase (GS) play important roles in N assimilation under low-nitrogen conditions

Surveyed references genes with their amplification and expression characteristics in <i>B. juncea.</i>

#<p>- used for normalization validation during abiotic stress conditions.</p