A multi-dimensional approach from seed-to-seed to understand and improve heat stress tolerance in rice

In changing climatic conditions, stress caused by high temperature poses a serious threat to rice cultivation. Physiological, biochemical, and molecular analysis of rice cultivars revealed that Nagina22 (N22) shows lesser reduction in chlorophyll content, net photosynthetic rate, spikelet fertility and grain yield, but increased membrane thermal stability, antioxidant enzymes activity and transpiration rate (E) at high temperature. DREB, RAB, LEA, and genes associated with hormones signalling were induced during germination, while OsFd (an iron sulphur cluster binding protein) and CWIP (cell wall integrity protein) emerged as high priority candidate genes in seedling and reproductive stages. Their function is being analysed by transgene expression and CRISPR/Cas genome editing approaches. Field screening in polyhouse, late sowing and temperature gradient chamber for 20 morpho-physiological traits indicated the importance of both yield and spikelet fertility, and photosynthesis traits. N22 showed the least Heat Susceptibility Index (HSI) for yield/plant, spikelet fertility, flag leaf SPAD and stomatal conductance, while Vandana showed the highest HSI for spikelet fertility and flag leaf temperature. QTLs for HSI of spikelet fertility were identified on chromosome 1 and HSI of yield per plant on chromosomes 1, 2, 3, 4, 7 and 8; and PV of 6% to 57% using 174 F2-3 Vandana x N22 mapping population. Simultaneously, RNAseq was performed to identify the genome wide miRNAs and transcriptome of N22 and Vandana from shoot and root after short and long duration of heat stress treatments; and recovery phase for an eQTL-guided function-related co-expression analysis to identify the putative regulators and gene regulatory networks

A deep study on real-time atmospheric aerosols and variability over Indian subcontinent environment

Study of atmospheric aerosols is very complex owing to their short life time and, chemical constituents. Aerosol loading is highly regional and there life time is very short. An attempt has been made in this paper to study the variability of atmospheric aerosols over Indian subcontinent using a statistical parameter Coefficient of Variation (COV). The magnitude of variability over this region is studied. The factors influencing the variability are studied to find the reasons for difference in magnitude over different regions. Rainfall naturally influences the variability aerosols due to scavenging, but if it is the only factor influencing the variability, the study is absurd. It is found that the influence of rainfall on COV is not pronounced as it is not a seasonal phenomenon. Influence of other parameters viz. Topography, wind vector, thermal power plants and population on variability of aerosols is clearly found. These results help in classifying aerosol zones on the basis of variability of aerosol optical depth. The study also helps in finding the cause of aerosol loading over a region. Measures can be taken to decrease the loading if it is due to local sources

Lidar observations of sodium layer over low latitude, Gadanki (13.5° N, 79.2° E): seasonal and nocturnal variations

In this paper, we present seasonal and nocturnal variations of mesospheric sodium (Na) layer parameters observed over Gadanki (13.5° N, 79.2° E), based on 166 nights during the period from January 2005 to December 2006, for the first time. The total Na content decreases during the evening and reaches a minimum value around midnight and maximum in the early morning. The year-to-year variations illustrate that Na layers reach the peak value close to 93.5 km for the year 2005 and ~93 km for the year 2006 and falls to near zero value around 110 km. Though, seasonal variation of sodium density illustrate maximum values in September, December and March, we require a larger data base for September months to conclude the statement. The column abundance shows maximum during autumn equinox and minimum during winter. The obtained seasonal and nocturnal variation of sodium layer parameters are compared with mid-latitude observations and further possible mechanisms are discussed

Not Available

Not AvailableComputational prediction of potential miRNAs and their target genes was performed to identify the miRNAs and genes associated with temperature response in rice. The data of temperatureresponsive miRNAs of Arabidopsis, and miRNAs and whole genome data of rice were used to predict potential miRNAs in O. sativa involved in temperature response. A total of 55 miRNAs were common in both the species. A total of 27 miRNAs were predicted at the first time in rice. Target genes were searched for these 27 miRNAs in rice genome following stringent criteria. Real time PCR based on expression analysis of nine miRNAs showed that majority of the miRNAs were down regulated under heat stress for rice cultivar Nagina 22. Furthermore, miR169, miR1884 and miR160 showed differential expression in root and shoot tissues of rice.Identification and expression studies of miRNAs duringheat stress will advance the understanding of gene regulation under stress in rice.Not Availabl

Not Available

Not AvailableComputational prediction of potential microRNAs (miRNAs) and their target genes was performed to identify the miRNAs and genes associated with temperature response in rice. The data of temperature-responsive miRNAs of Arabidopsis, and miRNAs and the whole genome data of rice were used to predict potential miRNAs in Oryza sativa involved in temperature response. A total of 55 miRNAs were common in both the species, and 27 miRNAs were predicted at the first time in rice. Target genes were searched for these 27 miRNAs in rice genome following stringent criteria. Real time PCR based on expression analysis of nine miRNAs showed that majority of the miRNAs were down regulated under heat stress for rice cultivar Nagina 22. Furthermore, miR169, miR1884 and miR160 showed differential expression in root and shoot tissues of rice. Identification and expression studies of miRNAs during heat stress will advance the understanding of gene regulation under stress in rice.Not Availabl

Not Available

Not AvailableIn changing climate scenario, heat stress caused by increased atmospheric CO2 is a major concern for rice productivity. There is a need to decipher the mechanisms of heat stress susceptibility and tolerance response of rice cultivars considering that high temperature is detrimental to growth and development of rice crop. The present study was designed to understand the heat stress response in heat-susceptible (Vandana) and heat-tolerant (N22) cultivars of rice. Rice seedlings were subjected to short-duration (24 h, SDS) and long-duration (5 days, LDS) heat stress (42 °C/36 °C, day/night). Besides the heat stress, recovery response (REC) of both the cultivars was also studied. Physiological parameters (chlorophyll content and membrane thermostability) and root/shoot length analysis revealed that N22 has better efficiency in recovering from heat stress. In particular, root tissue of N22 showed increased thermotolerance during SDS and LDS when compared with Vandana. In addition to physiological studies, gene expression pattern of 13 genes including heat shock transcription factors and heat shock proteins and 9 microRNAs (miRNAs) was analyzed in root and shoot of both the genotypes during various treatments. Gene and miRNA expression studies showed that root tissue of N22 was more responsive during SDS and LDS, suggesting important function of roots in heat stress tolerance. Further, during recovery, root tissue of both the genotypes showed more significant change in gene expression than shoot which signifies the vital role of plant root system in heat stress recovery response. Very high expression of an unknown iron-sulfur cluster-binding protein OsFd involved in electron transport activity was observed in root tissue of N22 during all the stress treatments. This study shows that better recovery and efficient root system play an important role in heat tolerance trait of N22.Not Availabl

Not Available

Not AvailableMicroRNAs (miRNAs) are known to regulate expression of genes under stress. We report here the deep sequencing of small RNAs expressed during control, short and prolonged heat stress and recovery. Genome-wide identification of miRNAs in tolerant (Nagina 22) and susceptible (Vandana) rice cultivars was performed in 16 samples representing root and shoot of 13-day-old seedlings.The expression profile of miRNAs was analysed in 36 pairwise combinations to identify the genotype-, treatment- and tissue-dependent expression of miRNAs. Small-RNA sequencing of 16 libraries yielded ~271 million high-quality raw sequences; 162 miRNA families were identified. The highly expressed miRNAs in rice tissues were miR166, miR168, miR1425, miR529, mR162, miR1876, and miR1862. Expression of osamiR1436, osa-miR5076, osa-miR5161, and osa-miR6253 was observed only in stressed tissue of both genotypes indicating their general role in heat stress response.Expression of osa-miR1439, osa-miR1848, osa-miR2096, osamiR2106, osa-miR2875, osa miR3981, osa-miR5079, osa-miR5151, osa-miR5484, osa-miR5792, and osa-miR5812 was observed only in Nagina 22 during high temperature, suggesting a specific role of these miRNAs in heat stress tolerance. This study provides details of the repertoire of miRNAs expressed in root and shoot of heat susceptible and tolerant rice genotypes under heat stress and recovery.Not Availabl

Not Available

Not AvailableAbstract Increasing episodes of high temperature (HT) is becoming a serious threat to rice production throughout the world. Studies on the response of popular rice varieties to HT stress in natural field conditions are very limited. Hence, we tested six popular rice varieties for their response to HT stress imposed by late sowing under field conditions. Effect of heat stress was evaluated based on the following traits: flag leaf chlorophyll content (SPAD), flag leaf temperature, net photosynthetic rate (PN), stomatal conductance (gs), spikelet fertility and yield per plant (YPP). High temperature stress decreased overall spikelet fertility by 16% and yield per plant by 29%. Based on the heat susceptibility index (HSI) of all the traits, Nagina22 and a restorer line KMR3 were identified as highly tolerant and a high yielding mega variety BPT5204 and a drought tolerant cultivar Vandana were identified as highly susceptible to heat stress. Further, HSI values for SPAD, PN and YPP showed significant correlation indicating that these traits are highly useful in screening genotypes for HT stress in late sown conditions.Not Availabl

Trait and Marker Associations in Oryza nivara and O. rufipogon Derived Rice Lines under Two Different Heat Stress Conditions

Wild species and derived introgression lines (ILs) are a good source of genes for improving complex traits such as heat tolerance. The effect of heat stress on 18 yield traits was studied in four treatments in two seasons, under field conditions by subjecting 37 ILs and recurrent parents Swarna and KMR3, N22 mutants, and wild type and 2 improved rice cultivars to heat stress using polycover house method in wet season and late sowing method in dry season. Normal grown unstressed plants were controls. Both correlation and path coefficient analysis showed that the major contributing traits for high yield per plant (YPP) under heat stress conditions were tiller number, secondary branches in panicle, filled grain number, and percent spikelet fertility. Three ILs, K-377-24, K-16-3, and S-148 which gave the highest YPP of 12.30–32.52 g under heat stress in both the seasons were considered the most heat tolerant. In contrast, K-363-12, S-75, and Vandana which gave the least YPP of 5.36–10.84 g were considered heat susceptible. These lines are a good genetic resource for basic and applied studies on heat tolerance in rice. Genotyping using 49 SSR markers and single marker analysis (SMA) revealed 613 significant marker- trait associations in all four treatments. Significantly, nine markers (RM243, RM517, RM225, RM518, RM525, RM195, RM282, RM489, and RM570) on chromosomes 1, 2, 3, 4, 6, and 8 showed association with six traits (flag leaf spad, flag leaf thickness, vegetative leaf temperature, plant height, panicle number, and tiller number) under heat stress conditions in both wet and dry seasons. Genes such as heat shock protein binding DnaJ, Hsp70, and temperature-induced lipocalin-2 OsTIL-2 close to these markers are candidates for expression studies and evaluation for use in marker assisted selection for heat tolerance

Not Available

Not AvailableIn changing climate scenario, heat stress caused by increased atmospheric CO2 is a major concern for rice productivity. There is a need to decipher the mechanisms of heat stress susceptibility and tolerance response of rice cultivars considering that high temperature is detrimental to growth and development of rice crop. The present study was designed to understand the heat stress response in heat-susceptible (Vandana) and heat-tolerant (N22) cultivars of rice. Rice seedlings were subjected to short-duration (24 h, SDS) and longduration (5 days, LDS) heat stress (42 °C/36 °C, day/night). Besides the heat stress, recovery response (REC) of both the cultivars was also studied. Physiological parameters (chlorophyll content and membrane thermostability) and root/shoot length analysis revealed that N22 has better efficiency in recovering from heat stress. In particular, root tissue of N22 showed increased thermotolerance during SDS and LDS when compared with Vandana. In addition to physiological studies, gene expression pattern of 13 genes including heat shock transcription factors and heat shock proteins and 9 microRNAs (miRNAs) was analyzed in root and shoot of both the genotypes during various treatments. Gene and miRNA expression studies showed that root tissue of N22 was more responsive during SDS and LDS, suggesting important function of roots in heat stress tolerance. Further, during recovery, root tissue of both the genotypes showed more significant change in gene expression than shoot which signifies the vital role of plant root system in heat stress recovery response. Very high expression of an unknown iron-sulfur cluster-binding protein OsFd involved in electron transport activity was observed in root tissue of N22 during all the stress treatments. This study shows that better recovery and efficient root system play an important role in heat tolerance trait of N22.Not Availabl