Plant Gene and Traits 2024, Vol.15, No.3, 108-117 http://genbreedpublisher.com/index.php/pgt 108 Review and Perspectives Open Access Biochemical Pathways of Starch Synthesis in Cassava: Genetic Bases and Breeding Implications JiongFu Hainan Institute of Tropical Agricultural Resources (HITAR), Sanya, 572025, Hainan, China Corresponding email: Jim.xj.fang@hitar.org Plant Gene and Trait, 2024, Vol.15, No.3 doi: 10.5376/pgt.2024.15.0012 Received: 01 Mar., 2024 Accepted: 05 Apr., 2024 Published: 08 May., 2024 Copyright © 2024 Fu, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Fu J., 2024, Biochemical pathways of starch synthesis in cassava: genetic bases and breeding implications, Plant Gene and Trait, 15(3): 108-117 (doi: 10.5376/pgt.2024.15.0012) Abstract This systematic review aims to integrate current knowledge on the biochemical pathways of starch synthesis in cassava (Manihot esculenta Crantz), elucidate the genetic bases underlying these processes, and discuss the implications for breeding programs aimed at improving cassava starch quality. Recent studies have identified a total of 45 genes involved in starch biosynthesis in cassava, including key enzymes such as ADPG pyrophosphorylase (AGPase), granule bound starch synthase (GBSS), and starch branching enzyme (SBE). These genes play crucial roles in determining the content and structure of amylose and amylopectin, which are vital for the starch's unique properties in food processing and industrial applications. Additionally, 110 quantitative trait loci (QTLs) associated with starch content and pasting properties have been identified, offering valuable markers for breeding efforts. Comparative genomic analyses have revealed positive selection for genes related to photosynthesis and starch accumulation, as well as negative selection for genes involved in cell wall biosynthesis and secondary metabolism, including cyanogenic glucoside formation in cultivated cassava varieties. Furthermore, the reconstructed metabolic pathway of starch biosynthesis in cassava provides a framework for integrating omics data, which has demonstrated distinct activities of the pathway at different stages of root development. The findings from this review highlight the significant progress made in understanding the genetic and biochemical aspects of starch synthesis in cassava. These advancements not only contribute to the fundamental knowledge of cassava biology but also have the potential to significantly impact breeding programs by providing molecular tools and insights for the development of cassava varieties with improved starch quality. Keywords Cassava (Manihot esculenta Crantz); Starch synthesis; Biochemical pathways; Genetic variation; Breeding; Quantitative trait loci (QTLs); Gene expression 1 Introduction Cassava (Manihot esculenta Crantz) is a root crop of paramount importance in tropical and subtropical regions, serving as a staple food for millions of people. Its significance is attributed to its high carbohydrate content, adaptability to diverse environments, and potential for high carbohydrate production (Wang et al., 2014). As a staple, cassava plays a crucial role in food security and is a primary source of energy for populations in these regions. Beyond its role in human nutrition, cassava starch is a versatile material with a wide range of applications in food processing and industrial sectors due to its unique properties (Tappiban et al., 2019). Starch, the most important carbohydrate source in plant species, consists of amylose and amylopectin, which determine its physicochemical properties and functionality (Tappiban et al., 2019). The economic and nutritional value of starch in cassava cannot be overstated, as it is the key determinant of the crop's quality for both consumption and industrial use. Understanding the biosynthesis of starch in cassava is therefore essential for improving its quality and tailoring it to specific needs. The objective of this systematic review is to elucidate the biochemical pathways of starch synthesis in cassava, explore the genetic foundations underlying these processes, and discuss the implications for breeding programs. Recent advances have shed light on the identification of genes and enzymes involved in starch biosynthesis, as well as the mechanisms of gene regulation during root development (Tappiban et al., 2019). Comparative genomic analyses have revealed selection pressures on genes related to starch accumulation, which are a result of natural selection and domestication (Wang et al., 2014). Furthermore, genetic modification strategies have demonstrated
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