Transcriptome dynamics of rice spikelets under heat stress treatment

Rice reproductive development is highly sensitive to high temperature stress. In rice flowering occurs over a period of at least 5 days. Heat stress alters the global gene expression dynamics in panicle especially during pollen development, anthesis and grain filling. Some of the rice genotypes like Nagina 22 show better spikelet fertility and grain filling compared to high yielding and popular rice cultivars like IR 64. We carried out microarray analysis of 8 days heat stressed panicles of Nagina22, heat and drought tolerant aus rice cultivar and IR64, a heat susceptible indica genotype along with unstressed samples of Nagina22 and IR64 so as to understand the transcriptome dynamics in these two genotypes under heat stress and to identify the genes important for governing heat stress tolerance in rice. Both the genotypes were grown in temperature controlled phenotyping facility and staggered planting was used to synchronize their flowering time. Once the plants entered the booting stage they were tagged and the temperature inside the facility was increased to 5 °C more than the atmospheric temperature prevailing. The panicles from the tagged main tillers were collected after 8 days of heat stress. For control, samples grown in the open adjacent field and tagged on booting were collected on the same day. All possible comparisons of the data were made to understand the differentially expressed genes under heat stress that are specific to Nagina 22.