Expression analysis of two reverse duplicated small heat shock protein genes in rice (Oryza sativa L.)

The small heat shock protein (sHSP) chaperones are required for protecting cellular proteins from damage, as well as re-folding denatured proteins. This study was carried out to investigate the temporal-spatial expression patterns of two sHSP genes in rice. These two genes, named as Os16.9A and Os16.9B, are reverse duplicated genes that adjacently located on chromosome 1 and probably share the same or overlapping DNA region as a promoter. The interval sequence between the start codons of the two genes which are transcribed in opposite directions is only about 2.6 kb. Semi-quantitative RT-PCR was carried out to detect the expression of the two genes under normal growth conditions and different stress conditions. The expression patterns of the two genes were in detail investigated by using β-glucuronidase (GUS) reporter gene fusion system. Results showed that heat shock stress can induce high level expression of the two genes. Under normal growth conditions, Os16.9A and Os16.9B expressed in vegetative organs and young panicles. GUS staining combined with cytological observations showed that the two genes expressed mainly in the vascular tissues of roots, stems and young panicles, implicating that Os16.9A and Os16.9B play important roles not only for heat shock response, but also for normal development in rice.