Abstract
Grain quality is one of the key targets to be improved for rice breeders and covers cooking, eating, nutritional, appearance, milling, and sensory properties. Cooking and eating quality are mostly of concern to consumers and mainly determined by starch structure and composition. Although many starch synthesis enzymes have been identified and starch synthesis system has been established for a long time, novel functions of some starch synthesis genes have continually been found, and many important regulatory factors for seed development and grain quality control have recently been identified. Here, we summarize the progress in this field as comprehensively as possible and hopefully reveal some underlying molecular mechanisms controlling eating quality in rice. The regulatory network of amylose content (AC) determination is emphasized, as AC is the most important index for rice eating quality (REQ). Moreover, the regulatory mechanism of REQ, especially AC influenced by high temperature which is concerned as a most harmful environmental factor during grain filling is highlighted in this review.
Highlights
Rice is one of the most important staple foods, feeding more than half of the population in the world
Genetic studies using different populations, such as doubled haploid (DH), recombinant inbred lines (RILs), BCmFn, and chromosome segment substitution lines (CSSLs), have been performed (Huang et al, 2000; Lanceras et al, 2000; Li et al, 2003, 2011; Septiningsih et al, 2003; Fan et al, 2005; Guo et al, 2007; Zheng et al, 2008; Liu et al, 2011; Zhang et al, 2020a), and a series of quantitative trait loci (QTLs) and/or genes for amylose content (AC) have been identified in the rice genome in the past few decades (Table 1; He et al, 1999; Tan et al, 1999; Bao et al, 2002; Wang et al, 2007a; Pandey et al, 2012; Fasahat et al, 2014; TakemotoKuno et al, 2015; Lau et al, 2016)
The ss1/ ss3a double mutant of japonica rice is sterile (Fujita et al, 2011; Hanashiro et al, 2011). These data indicated that the reduction of short chains in AP might not be enough for morphological alteration of starch granules, while the simultaneous reduction of both short and long chains could affect the formation of starch granules
Summary
Rice is one of the most important staple foods, feeding more than half of the population in the world. Starch accounts for more than 80% of the storage material in the rice endosperm and is composed of 10–30% amylose (AM) and 70–90% amylopectin (AP). Rice eating quality (REQ) is mainly assessed by three main physicochemical characteristics: the amylose content (AC), gel consistency (GC), and gelatinization temperature (GT; Juliano, 1985). The AC is the most important index for REQ, as it is the key determinant of the firmness and sticky nature of cooked rice (Tian et al, 2009; Tao et al, 2019). Starch Biosynthesis and Rice Quality Control years, certain novel functions of some starch synthesis genes have been revealed, and many genes involved in the regulation of seed development have been isolated. To obtain a comprehensive understanding of starch synthesis in rice, this review summarizes previous studies and hopefully uncovers some important regulatory mechanisms of seed development and quality control. The molecular regulation of rice quality, especially the AC, will be highlighted in this review
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