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

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

Expression levels of 12 reference control genes across five experimental sets of <i>B. juncea</i> using geNorm.

*<p>- mean of Ct values from all analyzed samples in individual experimental sets along with the standard deviations (SD) observed.</p

The optimal number of reference genes required for effective normalization in each experimental sets of <i>B. juncea</i>.

<p>The pairwise variation (Vn/Vn+1) was analyzed between normalization factors NFn and NFn+1 by geNorm program to determined the optimal number of reference genes.</p

Expression stability of the 12 reference control genes of <i>B. juncea</i> as calculated by Normfinder.

<p>Expression stability of the 12 reference control genes of <i>B. juncea</i> as calculated by Normfinder.</p

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

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

Gene expression stability of the 12 candidate genes of <i>B. juncea</i> as predicted by geNorm.

<p>Mean expression stability (M) following stepwise exclusion of the least stable gene across all the samples within an experimental set. The least stable genes are on the left, and the most stable on the right.</p

Relative quantification of <i>BjDREB</i>-2 expression using identified stable reference genes and their combination for normalization under various stress conditions.

<p>Relative quantification of <i>BjDREB</i>-2 expression using identified stable reference genes and their combination for normalization under various stress conditions.</p