Abstract
Wheat (Triticum aestivum L.) is a temperate cereal with an optimum temperature range of 15–22°C during the grain filling stage. Heat stress is one of the major environmental constraints for wheat production worldwide. Temperatures above 25°C during the grain filling stage significantly reduced wheat yield and quality. This reduction was reported due to the inactivation of the soluble starch synthase, a key heat-labile enzyme in starch transformation of wheat endosperm. To improve wheat productivity under heat stress, the rice soluble starch synthase I, under the control of either a constitutive promoter or an endosperm-specific promoter, was expressed in wheat and the transgenic lines were monitored for expression and the effects on yield-related traits. The results showed that the transgenic wheat events expressed rice soluble starch synthase I at a high level after four generations, and transgenic plants produced grains of greater weight during heat stress. Under heat stress conditions, the thousand kernel weight increased 21–34% in T2 and T3 transgenic plants compared to the non-transgenic control plants. In addition, the photosynthetic duration of transgenic wheat was longer than in non-transgenic controls. This study demonstrated that the engineering of a heat tolerant soluble starch synthase gene can be a potential strategy to improve wheat yield under heat stress conditions.
Highlights
Wheat (Triticum aestivum L.) is one of the most important main food crops worldwide
Comparison between wheat and rice synthase I (SSI) genes The SSI enzyme is responsible for the elongation of shorter A and B1 chains during starch biosynthesis in the soluble phase of the amylopectin (Commuri and Keeling 2001; Fujita et al 2006) and the inactivation or destruction of this gene can result in a significant impact on crystalline amylopectin matrix formation, as well as grain filling
Using a novel scoring algorithm to compare relative thermostability of proteins using an integrated statistical and machine learning approach (Li et al 2010), it was predicted that the rice SSI protein was more thermostable than the wheat SSI protein
Summary
Wheat (Triticum aestivum L.) is one of the most important main food crops worldwide. It provides approximately 20% of the calories consumed by humans (Pfeifer et al 2014). Given the socioeconomic importance of wheat, many efforts of breeding have focused on improving its yield, quality, and adaptability to biotic and abiotic stresses. It is reported that for every 1°C rise above the optimum temperature during the grain filling stage, wheat yield is reduced 3 to 4% (Wardlaw et al 1989). Ever-increasing evidence in the past decades has demonstrated that elevated temperature during wheat anthesis and grain filling stages significantly reduces grain yield (Bhullar and Jenner 1986a; Keeling et al 1993; Farooq et al 2011; Prasad and Djanaguiraman 2014).
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