HSP101 alleles from indica and japonica subspecies of rice (Oryza sativa L.) show differential response to heat stress.

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conclusionHSP101 from IR64 (indica) rice is more effective at resolving protein aggregates in yeast as compared to Nipponbare (japonica). A newly developed dCAPS marker can distinguish polymorphism in HSP101 coding region. Rice is a staple crop that feeds more than 50% of the world's population and heat stress significantly impacts its yield. The heat shock protein ClpB1/HSP101 plays a crucial role in the survival of plants under heat stress. We have recently reported HSP101 polymorphism between two Asian rice subspecies indica and japonica by examining the 3K rice genomes. Here, we confirm the polymorphism by resequencing HSP101 and report the functional significance of HSP101 polymorphism during heat stress by expressing the protein coding regions of HSP101 from IR64 (indica) and Nipponbare (japonica) rice types in yeast and Arabidopsis thaliana. For transformation in Arabidopsis, we used the constitutively expressing 2XCaMV35S promoter to drive the expression in the trans-hosts. Variable HSP101 expression levels occurred in the transformed Arabidopsis progenies and, as a result, we could not note a clear-cut differential response of the two forms in providing heat tolerance to transformed plants. Using a heat-inducible yeast HSP104 promoter, we expressed two isoforms of HSP101 in yeast cells containing GFP-tagged RNQ prion. The RNQ-GFP aggregation was reduced to a significantly higher extent in yeast cells expressing the IR64 HSP101 compared to the yeast cells transformed with Nipponbare HSP101. We developed a dCAPS marker to distinguish the indica and japonica HSP101 alleles.