RNA-seq reveals the involvement of key genes for aerobic adaptation in rice

Adaptation of rice to the aerobic condition is needed to cope with the water scarcity as well as to ensure sustainable yield in future. To understand the molecular mechanisms responsible for aerobic adaptation in rice, we performed RNA-seq analysis of root and shoot i.e. developing panicle tissues at panicle initiation stage in two cultivars adapted to aerobic (CR Dhan 202) and traditional transplanted anaerobic (BPT 5204) conditions. The RNA-seq data emanated from 1.65 billion clean reads with approximately 37 million reads per sample. The number of differentially expressed transcripts was higher in the root than that in the shoot under both aerobic and anaerobic conditions. The transcription factors viz. MADS4, MADS5, MADS6, MADS7, MADS15 and transporters involved in sugar (SWEET3A) and nutrient uptake (PHT1;6, MDR-like ABC and vacuolar iron transporter homolog 2) were highly and uniquely expressed in the aerobic adapted cultivar (AAC) CR Dhan 202 under aerobic condition indicating their role in adaptation. The hormones such as ethylene and abscisic acid might be significantly involved in imparting aerobic adaptation. The higher expression of root related genes in the AAC under aerobic conditions suggests the involvement and sensitivity of roots to the water limiting condition. The metabolic activities are also more pronounced in the roots which impart rigorous plant establishment under the aerobic condition. The presence of alternative splice variants in the transcripts viz. Tetratrico peptide repeat (TPR) domain containing protein and GOLDEN2-LIKE1 (GLK1) additionally confirms that post transcriptional regulation is also crucial for aerobic adaptation. The QTLs related to root traits and stress tolerance harboring the uniquely expressed genes, which were identified in the present study can be deployed in molecular breeding programs to develop elite, high yielding aerobic rice cultivars.