Small heat shock proteins: key genes for regulating heat stress responses in rice

Small heat shock proteins (HSPs) play an important role in rice plants by protecting cells from thermal damage during heat stress (HS). Although various types of heat-tolerant small HSPs have been reported in rice, the key genes (KGs) for HS in rice remain elusive. Hence, in this investigation, we selected 23 critical small HSPs of rice response to HS from the literature and sorted out six uncloned KGs (OsHSP23.6, OsHSP26.2, OsHSP22.3, OsHSP18.6, OsHSP23.2, and OsHSP16.0) by analyzing five CytoHubba algorithms, including degree, closeness, bottleneck, MCC, and DMNC. The KGs expression results revealed that the six KGs are heat-induced heat-tolerant genes and play crucial roles in rice responses to HS. Moreover, GO (gene ontology) enrichment pathway analysis found that the KGs are involved in responses to reactive oxygen species (ROS), response to heat, unfolded protein binding, and protein folding. The expressology tree analysis indicated that the six KGs might have various functions under development and stress conditions. The tissue specific expression patterns exhibited the various expression levels of six KGs in different tissues under abiotic stress, including temperature stress. Relative gene expression results revealed that these KGs are heat-inducible and play critical roles to tolerate heat stress in rice. Therefore, these KGs have potential roles in the development of heat-tolerant varieties.