Integrated Expression Analysis of Small RNA, Degradome and Microarray Reveals Complex Regulatory Action of miRNA during Prolonged Shade in Swarnaprabha Rice.

Prolonged shade during the reproductive stage can result in significant yield losses in rice. For this study, we elucidated the role of microRNAs in prolonged-shade tolerance (~20 days of shade) in a shade-tolerant rice variety, Swarnaprabha (SP), in its reproductive stage using small RNA and degradome sequencing with expression analysis using microarray and qRT-PCR. This study demonstrates that miRNA (miR) regulation for shade-tolerance predominately comprises the deactivation of the miR itself, leading to the upregulation of their targets. Up- and downregulated differentially expressed miRs (DEms) presented drastic differences in the category of targets based on the function and pathway in which they are involved. Moreover, neutrally regulated and uniquely expressed miRs also contributed to the shade-tolerance response by altering the differential expression of their targets, probably due to their differential binding affinities. The upregulated DEms mostly targeted the cell wall, membrane, cytoskeleton, and cellulose synthesis-related transcripts, and the downregulated DEms targeted the transcripts of photosynthesis, carbon and sugar metabolism, energy metabolism, and amino acid and protein metabolism. We identified 16 miRNAs with 21 target pairs, whose actions may significantly contribute to the shade-tolerance phenotype and sustainable yield of SP. The most notable among these were found to be miR5493-OsSLAC and miR5144-OsLOG1 for enhanced panicle size, miR5493-OsBRITTLE1-1 for grain formation, miR6245-OsCsIF9 for decreased stem mechanical strength, miR5487-OsGns9 and miR168b-OsCP1 for better pollen development, and miR172b-OsbHLH153 for hyponasty under shade.

Nano-pollution: Why it should worry us.

Nanoparticles are immensely diverse both in terms of quality and sources of emission into the environment. Nowadays, nanotechnologies are developing and growing at a rapid pace without specific rules and regulations, leading to a severe effect on environment and affecting the labours in outdoor and indoor workplaces. The continue and enormous use of NPs for industrial and commercial purposes, has put a pressing need to think whether the increasing use of these NPs could overcome the severe environmental effects and unknown human health risks. Only a few studies have been carried out to assess the toxic effect of these NPs resulting from their direct or indirect exposure. There is in an increasing clamour to consider environmental implications of NPs and to monitor the outcome of NP during use in biological testing. There remain many open questions for consideration. An adequate research is required to determine the real toxic effect of these NPs on environment and human health. In this review, we have discussed the negative effects of NPs on environment and biosphere at large and the future research required.

Exogenous brassinosteroid and jasmonic acid improve drought tolerance in Brassica rapa L. genotypes by modulating osmolytes, antioxidants and photosynthetic system.

KEY MESSAGE: Exogenously supplied BR and JA help KS101 and KBS3 genotypes of Brassica rapa to alleviate drought stress by modifying osmolyte concentration, levels of antioxidant enzymes and photosynthetic system. Oilseed plants are susceptible to drought stress and a significant loss in yield has been reported during recent decades. Thus, it is imperative to understand the various underlying drought response mechanisms in Brassica oilseed plants to formulate the sustainable strategies to protect the crop yield under water-limiting conditions. Phytohormones play a key role in fine-tuning various regulatory mechanisms for drought stress adaptation in plants, and the present study explores the response of several physiological stress markers by exogenous supplementation of 24-epibrassinolide (EBL) and jasmonic acid (JA) on two genotypes of Brassica rapa, KS101 and KBS3 under drought stress conditions. The exogenous application of BR and JA, separately or in combination, significantly alleviated the drought stress by improving photosynthetic rate, photosynthetic pigments, stomatal conductance, transpiration rate and antioxidant defence. We observed that concentration of different osmolytes increased and membrane damage significantly reduced by the application of BR and JA. The overall activity of antioxidant enzymes POD, CAT, GR, APX and CAT elevated during all the treatments, be it stress alone or in combination with BR and JA, compared to the control. However, we observed that the BR was much better in mitigating the drought stress compared to JA. Thus, the present study suggests that BR and JA supplementation improves the performance of B. rapa on exposure to drought stress, which hints at the critical role of BR and JA in improving crop productivity in drought-prone areas.

Low-light and its effects on crop yield: Genetic and genomic implications.

Shade indicates decreased sunlight. The agricultural importance of shade imparts to its deteriorative effect of crop yield. Rice is not only the most widely used food crop by a third of the population of the world, but it has also been established as the modelmonocot plant for study. This article describes several important aspects of shade on rice yield with appropriate examples in other plants such as Arabidopsis. To start with, how different environmental or growth conditions create shade is explained. Themorphological, physiological and biochemical characteristics due to different kinds of shade are selectively explained. The molecular characteristics of rice under shade from genetic, genomic and epigenetic studied are discussed. Signalling components for the manifestation of shade tolerance responses and their interconnection with other signalling networks and hormone pathway components are from recent reports. A list of genes, micro-RNAs and metabolites that are involved in shade responses is presented. Lastly, implications for sustainable yield under shade is discussed. This review will be useful not only for cutting-edge information on shade tolerance but will also build framework for upcoming new rice varieties with sustainable yield under shade.