Effects of environmental factors on cereal starch biosynthesis and composition

The aim of this review is to examine how the quantity and quality of starch in cereal endosperm is affected by abiotic stress. This is important because starch is the primary food source for humans, and its accumulation in cereal endosperm is a fundamental component of yield. Grain yield; however, is constrained under environmental stress with negative ramifications for agricultural productivity and sustainability. This is a significant and likely to be growing problem given that weather patterns are predicted to become increasingly extreme. In this review, we first describe starch structure and biosynthesis in the developing endosperm. Next, we outline how starch biosynthesis, content and composition are altered in response to drought, temperature extremes, salinity, nitrogen deficiency, elevated carbon dioxide and acidity. Our focus will be on the enzymes involved in the conversion of sucrose-to-starch, and how their activity is regulated at the transcriptional and post-translational level in response to certain stress. We then suggest experimental approaches for developing cereal germplasm that maintains productivity and grain quality under sub-optimal conditions. Finally, we conclude that there is an urgent need to elucidate the regulatory mechanisms that modulate starch biosynthetic enzyme activity in response to environmental extremes. (c) 2012 Elsevier Ltd. All rights reserved.