Nisar Ahmed1, Ian J Tetlow2, Sehar Nawaz1, Ahsan Iqbal1, Muhammad Mubin1, Muhammad Shah Nawaz ul Rehman1, Aisha Butt1, David A Lightfoot3, Masahiko Maekawa4. 1. Centre of Agricultural Biochemistry and Biotechnology (CABB), University of Agriculture, Faisalabad, 38040, Pakistan. 2. Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1. 3. Department of Plant, Soil and Agricultural Systems, Carbondale, IL62901, USA. 4. Institute of Plant Science and Resources, Okayama University, Kurashiki, 710-0046, Japan.
Abstract
BACKGROUND: High temperature during grain filling affects yield, starch amylose content and activity of starch biosynthesis enzymes in basmati rice. To investigate the physiological mechanisms underpinning the effects of high temperature on rice grain, basmati rice was grown under two temperature conditions - 32 and 22 °C - during grain filling. RESULTS: High temperature decreased the grain filling period from 32 to 26 days, reducing yield by 6%, and caused a reduction in total starch (3.1%) and amylose content (22%). Measurable activities of key enzymes involved in sucrose to starch conversion, sucrose synthase, ADP-glucose pyrophosphorylase, starch phosphorylase and soluble starch synthase in endosperms developed at 32 °C were lower than those at 22 °C compared with similar ripening stage on an endosperm basis. In particular, granule-bound starch synthase (GBSS) activity was significantly lower than corresponding activity in endosperms developing at 22 °C during all developmental stages analyzed. CONCLUSION: Results suggest changes in amylose/amylopectin ratio observed in plants grown at 32 °C was attributable to a reduction in activity of GBSS, the sole enzyme responsible for amylose biosynthesis.
BACKGROUND: High temperature during grain filling affects yield, starch amylose content and activity of starch biosynthesis enzymes in basmati rice. To investigate the physiological mechanisms underpinning the effects of high temperature on rice grain, basmati rice was grown under two temperature conditions - 32 and 22 °C - during grain filling. RESULTS: High temperature decreased the grain filling period from 32 to 26 days, reducing yield by 6%, and caused a reduction in total starch (3.1%) and amylose content (22%). Measurable activities of key enzymes involved in sucrose to starch conversion, sucrose synthase, ADP-glucose pyrophosphorylase, starch phosphorylase and soluble starch synthase in endosperms developed at 32 °C were lower than those at 22 °C compared with similar ripening stage on an endosperm basis. In particular, granule-bound starch synthase (GBSS) activity was significantly lower than corresponding activity in endosperms developing at 22 °C during all developmental stages analyzed. CONCLUSION: Results suggest changes in amylose/amylopectin ratio observed in plants grown at 32 °C was attributable to a reduction in activity of GBSS, the sole enzyme responsible for amylose biosynthesis.
Authors: Alphonsine Mukamuhirwa; Helena Persson Hovmalm; Hans Bolinsson; Rodomiro Ortiz; Obedi Nyamangyoku; Eva Johansson Journal: Int J Environ Res Public Health Date: 2019-03-22 Impact factor: 3.390