Transcriptional profiling of the leaves of near-isogenic rice lines with contrasting drought tolerance at the reproductive stage in response to water deficit

Different genes involved in ABA and calcium signaling in leaf tissue of rice NILs and the parent IR64 under different water-deficit treatments. 1: up-regulated; -1: down-regulated; blank: no change in expression; 10: IR77298-14-1-2-B tolerant NIL, i.e., IR77298-14-1-2-B-10; 13: IR77298-14-1-2-B susceptible NIL, i.e., IR77298-14-1-2-B-13; 18: IR77298-5-6-B tolerant NIL, i.e., IR77298-5-6-B-18; 11: IR77298-5-6-B susceptible NIL, i.e., IR77298-5-6-B-11; 0.2 and 0.5 FTSW are severe and mild water-deficit treatments (XLSX 46 kb

Identification of orthologous regions associated with tissue growth under water-limited conditions

Plant recovery from early season drought is related to the amount of biomass retained during stress and biomass production after the end of stress. Reduction in leaf expansion is one of the first responses to water deficit. It is assumed that the control of tissue development under water deficit contributes to traits such as early vigor, as well as maintenance of growth of reproductive organs. To dissect the underlying mechanisms controlling tissue expansion under water-limited conditions, we used a multilevel approach combining quantitative genetics and genomics. To identify orthologous genetic regions controlling tissue growth under water-limited conditions a series of QTL mapping and microarray gene expression studies were conducted in rice and maize. Results of differentially expressed genes from microarray experiments, QTLs and candidate genes related to growth in the different species are compared on consensus maps (within species) and then on synteny maps (between species), to identify common genetic regions between rice and maize

Genetic variability of drought-avoidance root traits in the mini-core germplasm collection of chickpea (Cicer arietinum L.).

Extensive and deep root systems have been recognized as one of the most important traits for improving chickpea (Cicer arietinum L.) productivity under progressively receding soil moisture conditions. However, available information on the range of variation for root traits is still limited. Genetic variability for the root traits was investigated using a cylinder culture system during two consecutive growth seasons in the mini-core germplasm collection of ICRISAT plus several wild relatives of chickpea. The largest genetic variability was observed at 35 days after sowing for root length density (RLD) (heritability, h 2 = 0.51 and 0.54) across seasons, and followed by the ratio of plant dry weight to root length density with h 2 of 0.37 and 0.50 for first and second season, respectively. The root growth of chickpea wild relatives was relatively poor compared to C. arietinum, except in case of C. reticulatum. An outstanding genotype, ICC 8261, which had the largest RLD and one of the deepest root system, was identified in chickpea mini-core germplasm collection. The accession ICC 4958 which was previously characterized as a source for drought avoidance in chickpea was confirmed as one with the most prolific and deep root system, although many superior accessions were also identified. The chickpea landraces collected from the Mediterranean and the west Asian region showed a significantly larger RLD than those from the south Asian region. In addition, the landraces originating from central Asia (former Soviet Union), characterized by arid agro-climatic conditions, also showed relatively larger RLD. As these regions are under-represented in the chickpea collection, they might be interesting areas for further germplasm exploration to identify new landraces with large RLD. The information on the genetic variability of chickpea root traits provides valuable baseline knowledge for further progress on the selection and breeding for drought avoidance root traits in chickpea

Environmental Response and Genomic Regions Correlated with Rice Root Growth and Yield under Drought in the OryzaSNP Panel across Multiple Study Systems

Funding: This research was funded by the Generation Challenge Program (GCP) project G3008.06, “Targeting Drought-Avoidance Root Traits to Enhance Rice Productivity under Water-Limited Environments". The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Comparative transcriptome analysis of AP2/EREBP gene family under normal and hormone treatments, and under two drought stresses in NILs setup by Aday Selection and IR64

The AP2/EREBP genes play various roles in developmental processes and in stress-related responses in plants. Genome-wide microarrays based on the gene expression profiles of the AP2/EREBP family were analyzed under conditions of normal growth and drought stress. The preferential expression of fifteen genes was observed in specific tissues, suggesting that these genes may play important roles in vegetative and reproductive stages of growth. A large number of redundant genes were differentially expressed following phytohormone treatments (NAA, GA3, KT, SA, JA, and ABA). To investigate the gene expression responses in the root, leaf, and panicle of three rice genotypes, two drought stress conditions were applied using the fraction of transpirable soil water (FTSW) under severe (0.2 FTSW), mild (0.5 FTSW), and control (1.0 FTSW) conditions. Following treatment, transcriptomic analysis using a 44-K oligoarray from Agilent was performed on all the tissue samples. We identified common and specific genes in all tissues from two near-isogenic lines, IR77298-14-1-2-B-10 (drought tolerant) and IR77298-14-1-2-B-13 (drought susceptible), under drought stress conditions. The majority of the genes that were activated in the IR77298-14-1-2-B-10 line were members of the AP2/EREBP gene family. Non-redundant genes (sixteen) were found in the drought-tolerant line, and four genes were selected as candidate novel reference genes because of their higher expression levels in IR77298-14-1-2-B-10. Most of the genes in the AP2, B3, and B5 subgroups were involved in the panicle under severe stress conditions, but genes from the B1 and B2 subgroups were down-regulated in the root. Of the four subfamilies, RAV exhibited the highest number of up-regulated genes (80%) in the panicle under severe stress conditions in the drought-tolerant line compared to Minghui 63 under normal conditions, and the gene structures of the RAV subfamily may be involved in the response to drought stress in the flowering stage. These results provide a useful reference for the cloning of candidate genes from the specific subgroup for further functional analysis

Effects of drought stress on legume symbiotic nitrogen fixation: Physiological mechanisms

1136-1141<span style="font-size: 13.5pt;mso-bidi-font-size:8.5pt;font-family:" times="" new="" roman","serif""="">Drought stress is one of the major factors affecting nitrogen fixation by legume-rhizobium symbiosis. Several mechanisms have been previously reported to be involved in the physiological response of symbiotic nitrogen fixation to drought <span style="font-size: 13.5pt;mso-bidi-font-size:8.5pt;font-family:" times="" new="" roman","serif""="">stress, i.e. carbon shortage and nodule carbon metabolism, oxygen limitation, and feedback regulation by the accumulation of N fixation products. The carbon shortage hypothesis was previously investigated by studying the combined effects of CO2 enrichment and water deficits on nodulation and N2 fixation in soybean. Under drought, in a genotype with drought tolerant N2 fixation, approximately four times the amount of 14C was allocated to nodules compared to a drought sensitive genotype. <span style="font-size: 13.5pt;mso-bidi-font-size:8.5pt;font-family:" arial","sans-serif""="">It was found that an important effect of CO2 enrichment of soybean under drought was an enhancement of photo assimilation, an increased partitioning of carbon to nodules, whose main effect was to sustain nodule growth, which helped sustain <span style="font-size: 13.5pt;mso-bidi-font-size:8.5pt;font-family:" times="" new="" roman","serif""="">N2 rates under soil water deficits. The interaction of nodule permeability to O2 and drought stress with N2 fixation was examined in soybean nodules and led to the overall conclusion that O2 limitation seems to be involved only in the initial stages of water deficit stresses in decreasing nodule activity. The involvement of ureides in the drought response of N2 fixation was initially suspected by an increased ureide concentration in shoots and nodules under drought leading to a negative feedback response between ureides and nodule activity. Direct evidence for inhibition of nitrogenase activity by its products, ureides and amides, supported this hypothesis. The overall conclusion was that all three physiological mechanisms are important in understanding the regulation of N2 fixation and its response of to soil drying. </span

Agriculture & Food Systems to 2050:Global Trends, Challenges and Opportunities

This book features a comprehensive foresight assessment, exploring the pressures — threats as well as opportunities — on the global agriculture & food systems between now and 2050. The overarching aim is to help readers understand the context, by analyzing global trends and anticipating change for better planning and constructing pathways from the present to the future by focusing on the right questions and problems. The book contextualizes the role of international agricultural research in addressing the complex challenges posed by UN 2030 Agenda and beyond, and identifies the decisions that scientific leaders, donors and policy makers need to take today, and in the years ahead, to ensure that a global population rising to nine billion or more combined with rising incomes and changing diets can be fed sustainably and equitably, in the face of the growing climate threats

Rice leaf growth and water potential are resilient to evaporative demand and soil water deficit once the effects of root system are neutralized

International audienceRice is known to be sensitive to soil water deficit and evaporative demand, with a greatest sensitivity of lowland-adapted genotypes. We have analysed the responses of plant water relations and of leaf elongation rate (LER) to soil water status and evaporative demand in seven rice genotypes belonging to different species, subspecies, either upland- or lowland-adapted. In the considered range of soil water potential (0 to -0.6 MPa), stomatal conductance was controlled in such a way that the daytime leaf water potential was similar in well-watered, droughted or flooded conditions (isohydric behaviour). A low sensitivity of LER to evaporative demand was observed in the same three conditions, with small differences between genotypes and lower sensitivity than in maize. The sensitivity of LER to soil water deficit was similar to that of maize. A tendency towards lower sensitivities was observed in upland than lowland genotypes but with smaller differences than expected. We conclude that leaf water status and leaf elongation of rice are not particularly sensitive to water deficit. The main origin of drought sensitivity in rice may be its poor root system, whose effect was alleviated in the study presented here by growing plants in pots whose soil was entirely colonized by roots of all genotypes