Comparative Study of Susceptible and Tolerant Genotype Reveals Efficient Recovery and Root System Contributes to Heat Stress Tolerance in Rice

Abstract

In 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.