Keywords: Rice, Gene expression, Days after pollination, Aroma, Principal component analysis, Semi quantitative reverse transcriptase-polymerase chain reaction
The method of grain-filling during seed developmental process in rice is a complex process with the metabolite, hormone and aroma levels changing almost each day after pollination. The present study focused on transcript profiling of genes related to aroma production in the grains of four aromatic rice cultivars, viz., Gobindobhog, Kalonunia, Tulaipanji and Radhunipagal against the non-aromatic cultivar IR-64, collected at the intervals of 10 days after pollination (DAP), 20 DAP and 30 DAP. The BADH2 expression was significantly high in IR-64 grains, while the genes like P5CS and OAT were highly expressed in the aromatic cultivars. The P5C-producing genes (P5CS, PDH and OAT), along with TPI and DAO were found to be mostly increasing with seed maturity in Gobindobhog and Radhunipagal, all the aroma concerning genes, except P5CS exhibited lower expression in Tulaipanji at maturity. Although SPDS and SPMS expressions were recorded to be down regulated at maturity in all the aromatic varieties, the lowest expression was registered in Tulaipanji at 30 DAP developmental stage. The principal component analyses indicated towards close relations amongst the aroma related genes like TPI, PDH and OAT, and between P5CS and P5CDH. The aroma content was the highest at the 30 DAP stage in all the aromatic cultivars and was almost undetected in IR-64, which could be well correlated with the genes under study. Overall, this is the first novel report highlighting the differential expression pattern of aroma producing genes in connection to aroma formation in developing grains of the examined rice varieties.
Financial assistance from Council of Scientific and Industrial Research (CSIR), Government of India, through the research Grant [38(1387)/14/EMR-II] to Dr. Aryadeep Roychoudhury is gratefully acknowledged. The authors would also like to acknowledge Chinsurah Rice Research Station, West Bengal, and Bidhan Chandra Krishi Viswa Vidyalaya (BCKV), West Bengal, for providing the seeds of all the aromatic as well as non-aromatic rice varieties used in this investigation. The authors also acknowledge the infrastructural facilities received from the BOOST Grant (335/WBBDC/IP-2/2013) of the Department of Biotechnology, Government of West Bengal.