Posttranslational Modification of Waxy to Genetically Improve Starch Quality in Rice Grain

Abstract

The waxy (Wx) gene, encoding the granule-bound starch synthase (GBSS), is responsible for amylose biosynthesis and plays a crucial role in defining eating and cooking quality. The waxy locus controls both the non-waxy and waxy rice phenotypes. Rice starch can be altered into various forms by either reducing or increasing the amylose content, depending on consumer preference and region. Low-amylose rice is preferred by consumers because of its softness and sticky appearance. A better way of improving crops other than downregulation and overexpression of a gene or genes may be achieved through the posttranslational modification of sites or regulatory enzymes that regulate them because of their significance. The impact of posttranslational GBSSI modifications on extra-long unit chains (ELCs) remains largely unknown. Numerous studies have been reported on different crops, such as wheat, maize, and barley, but the rice starch granule proteome remains largely unknown. There is a need to improve the yield of low-amylose rice by employing posttranslational modification of Wx, since the market demand is increasing every day in order to meet the market demand for low-amylose rice in the regional area that prefers low-amylose rice, particularly in China. In this review, we have conducted an in-depth review of waxy rice, starch properties, starch biosynthesis, and posttranslational modification of waxy protein to genetically improve starch quality in rice grains.

Finding the LMA needle in the wheat proteome haystack

“…Starch content and starch-related proteins are prominent in wheat grain; PTMs involved in starch quality have been reviewed (80). Our study lists numerous potential PTMs; this warrants more experiments to validate them and decipher their role in LMA response.…”

Post-genomics revolution in the design of premium quality rice in a high-yielding background to meet consumer demands in the 21st century

“…Figure 2 shows starch biosynthesis and mutants of important starch synthesis enzymes. The post-translational modification of these enzymes through phosphorylation, alternative splicing, and allosteric changes plays a vital role in modifying starch content and altering the amylose–amylopectin composition ( Huang et al., 2020b ; Adegoke et al., 2021 ). Table 1 shows various mutants with altered physicochemical properties.…”

“…In rice ECQ improvement, targeted gene silencing is an effective tool to manipulate biosynthetic pathways in a constitutive or tissue-specific manner to obtain the desired phenotype. For example, the Wx , SSI , SSII-2 , ALK , FAD2-1 , and Badh2 genes were suppressed by RNA interference, and the resulting transgenic rice showed improved ECQ traits compared with the wild type ( Li et al., 2018a ; Zhao et al., 2019 ; Chen et al., 2020 ; Adegoke et al., 2021 ). However, widespread adoption of transgenic crops carrying foreign genes faces roadblocks due to regulatory concerns about potential toxicity and allergenicity to humans, adverse effects on non-target organisms, evolution of resistant weeds and insects, and so forth.…”

Recent Research Advances in the Development of Chalkiness and Transparency in Rice

“…In previous studies on some dark endosperm mutant rice, it is found that some low enzymatic activity natural mutations or genetically modified low enzymatic activity proteins of GBSSI caused the rice to exhibit a translucent phenotype due to the synthesis of less amylose (below 13%). This suggests a direct correlation between GBSSI and rice transparency [36][37][38]. Zhang et al studied transgenic rice lines with GBSSI activity and found that AC was lower in rice lines with lower GBSSI activity, and the grains showed a milky opaque appearance.…”