Salicylic acid alleviates methyl viologen induced oxidative stress through transcriptional modulation of antioxidant genes in Zea mays L

Salicylic acid (SA) is an important growth regulator that participates in both biotic as well as abiotic stress re- sponse in plants. Both-biotic and abiotic stresses are characterized by elevated cellular reactive oxygen species (ROS). We examined the biochemical and molecular effects of SA on the ROS scavenging system in maize. Pre- treatment of maize plants with SA prior to stress, reduced electrolyte leakage, enhanced protein accumulation, improved root biomass and grain yield. SA application also led to a general enhancement in the biochemical activities of three major ROS scavenging antioxidant enzymes, viz. superoxide dismutase (SOD), catalase (CAT) and peroxidases (POX). However, corresponding transcripts of various antioxidant isozymes depicted a dynamic response for different SA doses. Under stress, pre-treatment with 0.5 mM SA led to enhanced expression of all the Sod genes analyzed while higher SA concentration repressed many Sod genes. Cat 1 showed clear dose- dependent repression in response to graded concentrations of SA, while Cat 3 showed inverse dose-dependent activation in response to graded concentrations of SA. Apx 1 was found to be up-regulated at 0.5 mM SA, while higher doses of SA, i.e. 1.0 and 1.5 mM led to its repression. All the three concentrations of SA repressed Apx 2 gene. Taken together, our results indicate that SA has the potential to alleviate oxidative stress in maize through biochemical and transcriptional modulation of ROS scavenging pathway. Also, the concentration of SA has a great bearing in its alleviating role, with lower concentrations (viz 0.5 mM) being more desirable

Begomovirus DNA replication and pathogenicity

Begomoviridae is the largest genus of the family of single stranded DNA plant viruses, Geminiviridae and is responsible for significant agro-economic losses worldwide. Its small single-stranded DNA genome primarily replicates by rolling circle replication (RCR) mode with the help of certain viral and host factors. The role of virus encoded Rep protein in initiation and immediate post-initiation phases of RCR has been the subject of various studies. We have identified many host proteins which interact with Rep protein of a member of Begomovirus, namely, Mungbean yellow mosaic India virus, thereby playing a role in viral DNA replication. Of these, the role of host RAD54 protein is significant as the rad54 mutant of Arabidopsis does not permit mini viral DNA replication. The plant hosts protect themselves from begomoviruses by activating RNA interference (RNAi) pathways targeted against the viruses. However, the virus can also sometime overcome this form of host defence by encoding RNA silencing suppressors, which attenuate host RNAi and are regarded as major pathogenicity determinants. The viral suppressors do not share any signature sequences and are structurally and mechanistically dissimilar. These can be detected effectively, only through specialized functional assays. In this review, we also point out the potential biotechnological applications of the suppressors and discuss about various possible containment strategies for begomoviruses, including an exciting new approach involving artificial micro- RNAs

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Not AvailableIn order to dissect the adaptation response of maize to heat-stress, we characterized and juxtaposed different physio-biochemical parameters for two contrasting genotypes, namely DTPYC9F119 (heat-stress tolerant) and K64R (heat-stress susceptible) under 6 days heat treatment (38/28 C). Chlorophyll a and b content was found to be reduced under high temperature in both the genotypes, but, it was reduced more prominently in the susceptible genotype (K64R). Net photosynthetic rate was significantly reduced under high temperature in K64R but this reduction was relatively lower in case of DTPYC9F119. Stomatal conductance was increased under stress treatment in both the genotypes but the rate of increase was lower in tolerant one (DTPYC9F119). Activity of anti-oxidant enzymes (viz. catalase, peroxidase and superoxide dismutase) and their gene expression was increased in both the genotypes under heat-stress condition. Thus, the heat-stress tolerant genotype has evolved some strategies like modulation of anti-oxidant gene expression, lower transpiration rate, lower increase of internal CO2 concentration which could make sustain a basic level of photosynthesis even under high temperature stress, etc. that may contribute to its tolerance trait.Not Availabl

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13th Asian Maize Conference organized jointly by ICAR, CIMMYT, IIMR, PAU and BISA at Ludhiana, India from 8-10 October, 2018The post green revolution agriculture is based on generous application of fertilizers and high-yielding genotypes. Maize cannot utilize more than 10% of the applied inorganic phosphate (Pi) which is a non-renewable fertilizer resource. Owing its emergence as an industrial, feed and food crop, improvement in phosphorus use efficiency (PUE) is highly essential in maize for sustainable use of phosphate containing fertilizers. Therefore, there is a need to identify key regulatory genes playing pivotal role in acquisition, transportation and utilization of Pi in maize. In this endeavor, the present study was undertaken to identify Pi-responsive genes in maize through whole-genome analysis and expression profiling. The twelve Pi-responsive genes (five having regulatory role, four encoding for secretory proteins and two encoding for Pi transporters) were identified through Hidden Markov Model-based homology search. The expression of identified genes in root and shoot tissues of hydroponically grown maize inbred line HKI-163 under Pi sufficient (1mM KH2PO4) and deficient (5µM KH2PO4) condition was analyzed using quantitative and semi-quantitiative RT-PCR. Expression analysis revealed that 11 out of 12 genes were significantly up or down regulated under Pi-deficient condition. To comment upon the mechanism of observed differential expression of Pi-responsive genes under phosphate deprived condition, cis-regulatory elements present in the upstream promoter region of these genes were analyzed and phosphate responsive elements were found in two genes. In other genes, the differential expression may be indirectly linked to phosphate deprivation. We believe that the identified Pi-responsive genes can be employed for engineering high PUE in maize after functional validation.ICAR, CIMMYT, IIMR, PAU and BIS

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In: abstract book of National Seminar on “Maize for Crop Diversification under Changing Climatic Scenario” jointly organized by MTAI, IIMR and PAU held at Ludhiana, February 9-10, 2020.The post green revolution agriculture is based on generous application of nitrogen (N)-based fertilizers and high-yielding genotypes. Generally, plants cannot utilize more than 40% of the applied nitrogenous fertilizer; hence more than half of the applied fertilizer is lost to the environment and results in environmental pollution via acidification, eutrophication, and depletion of ozone layer by emission of greenhouse gas. Therefore, genetic improvement in nitrogen use efficiency (NUE) in crops is desirable for a sustainable and profitable agriculture. There is a need to identify key regulatory factors playing pivotal role in acquisition, transportation and utilization of N in plants. Among other factors, microRNA (miRNA) mediated gene regulation plays a crucial role in controlling low N stress adaptation and tolerance in plants. In this endeavor, the present study was undertaken to identify N stress responsive miRNAs in maize in tropical maize using high-throughput sequencing. The HKI-163 maize inbred line was grown hydroponically with sufficient nitrogen (2mM) and without nitrogen for 21 days. Observations were recorded on all important shoot and root physiological parameters. The root and shoot samples were deep sequenced for miRNA study. The expression analysis revealed 23 known miRNAs (11 up & 12 down-regulated) in leaf and 3 known miRNAs (1 up & 2 down-regulated) in root, which expressed differentially under N stress. We also identified 53 (20 up & 33 down-regulated) and 26 (9 up & 17 down-regulated) novel miRNAs in leaf and roots respectively. The knowledge gained will help understand the important roles that miRNAs play in maize, while responding to a nitrogen limiting environment.Not Availabl

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International Conference on Climate Change, Biodiversity and Sustainable Agriculture (ICCBS-2018) organized jointly by Assam Agriculture University and Prof. H.S. Srivastava Foundation for Science held at Jorhat, Assam from 13th to 16th Dec 2018.Low phosphorus availability poses major constrain to crop yield by limiting plant growth in many Indian soil types (acidic, alkaline and calcareous). Cropping system is dependent on external application of phosphate fertilizers that is mainly (~90%) imported. Phosphorus is non-renewable natural resource and its global supply would start tapering off after 2030, thereby triggering a massive agricultural crisis. Phosphorus (P) is essential for normal growth and maturity as it plays important role in photosynthesis, respiration, energy storage and transfer, cell division, cell enlargement and several other processes in plants. Modern cereal genotypes, like, the single cross maize hybrids require a high dose of phosphate for optimum production. However, the plant is capable of utilizing only about 10% of the applied phosphorus. Due to its precipitation as aluminium phosphate, phosphorus availability is even more severely constrained in acidic soil of eastern and north-eastern India, where large acreage of maize is grown under upland with very low productivity. Thus, phosphorus availability is one of the most important production constraints in maize, especially in north eastern parts of India. Owing its emergence as an industrial, feed and food crop, improvement in phosphorus use efficiency (PUE) is highly essential in maize for sustainable use of phosphate containing fertilizers. Identification of key genes and their regulatory elements playing pivotal role in acquisition, transportation and utilization of phosphorus in maize can help in developing phosphorus efficient maize genotypes. MicroRNA-mediated gene regulation plays a crucial role in controlling low phosphorus stress adaptation and tolerance in plants. In this endeavour, the present study was undertaken to identify differentially expressed miRNAs under low phosphorus stress in tropical maize through NGS and expression profiling. The HKI-163 maize inbred line was grown hydroponically under sufficient (1mM KH2PO4) and deficient (5µM KH2PO4) phosphate conditions for 21 days. Observations were recorded on all important shoot and root physiological parameters. The phosphate content was measured in shoots and roots of the maize plants growing in both phosphate stressed and unstressed condition. The root and shoot samples were deep sequenced for miRNA study. The expression analysis revealed 35 known miRNAs (12 up & 23 down-regulated) in shoot and 27 known miRNAs (15 up & 12 down-regulated) in root expressed differentially under low phosphate stress. Among these, 10 miRNAs were common in roots and shoot/leaf tissue. We also identified 40 (18 up & 22 down-regulated) and 46 (37 up & 9 down-regulated) novel miRNAs in shoots and roots respectively. The deep sequencing result is being validated through stem-loop RT-PCR. This study will provide valuable insight into the role of miRNA in phosphate use efficiency in maize. The expression of key miRNA(s) identified from this study could be modulated / engineered to enhance phosphate utilization efficiency in maize plants.Assam Agriculture University and Prof. H.S. Srivastava Foundation for Scienc

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Not AvailableAgriculture is based on plant senescence. A crop must age and die in order for grain to be harvested. While this type of whole-plant senescence may be desirable for cereals, pulses, and annual oilseeds, many crops demand progressive senescence to facilitate an indeterminate or a semi determinate growth habit that is more amenable for multiple harvesting. At the same time, there are crops like multicut green fodder crops, where senescence may be even sometime considered a liability. Is plant senescence a necessary evil in agriculture? Can knowledge of coordinated biological steps leading to plant senescence be exploited to develop higher-yield and stress-tolerant crops? This chapter attempts to highlight the basic plant senescence process in relation to its relevance to agricultural crops. It further builds on the narrative of using fundamental senescence knowledge to translate superior agricultural products through the utilization of source-sink relationships, breeding stay-green genotypes and genetic-engineering pathways that modulate senescence. The examples provided here are in no way exhaustive, but are only meant to be illustrative. The premise of employing plant death in improving crops, which is what senescence is, is itself a fascinating journey.Not Availabl