Comprehensive analysis of AGPase genes uncovers their potential roles in starch biosynthesis in lotus seed

Abstract

Background Starch in the lotus seed contains a high proportion of amylose, which endows lotus seed a promising property in the development of hypoglycemic and low-glycemic index functional food. Currently, improving starch content is one of the major goals for seed-lotus breeding. ADP-glucose pyrophosphorylase (AGPase) plays an essential role in regulating starch biosynthesis in plants, but little is known about its characterization in lotus. Results We describe the nutritional compositions of lotus seed among 30 varieties with starch as a major component. Comparative transcriptome analysis showed that AGPase genes were differentially expressed in two varieties (CA and JX) with significant different starch content. Seven putative AGPase genes were identified in the lotus genome (Nelumbo nucifera Gaertn.), which could be grouped into two subfamilies. Selective pressure analysis indicated that purifying selection acted as a vital force in the evolution of AGPase genes. Expression analysis revealed that lotus AGPase genes have varying expression patterns, with NnAGPL2a and NnAGPS1a as the most predominantly expressed, especially in seed and rhizome. NnAGPL2a and NnAGPS1a were co-expressed with a number of starch and sucrose metabolism pathway related genes, and their expressions were accompanied by increased AGPase activity and starch content in lotus seed. Conclusions Seven AGPase genes were characterized in lotus, with NnAGPL2a and NnAGPS1a, as the key genes involved in starch biosynthesis in lotus seed. These results considerably extend our understanding on lotus AGPase genes and provide theoretical basis for breeding new lotus varieties with high-starch content.

Genome-Wide Characterization and Comprehensive Analysis of NAC Transcription Factor Family in Nelumbo nucifera

“…Multiple complex pathways respond to different plant signals in a coordinated manner that involves the recruitment of various transcription factors ( Li et al, 2018b ; Sun et al, 2020 ). The published transcriptome data of seed cotyledons at 9, 12 and 15 DAP in “China Antique” (CA) and “Jianxuan 17” (JX) were used to investigate the possible roles of NnNACs in lotus seed development.…”

“…( Ming et al, 2013 ; Sun et al, 2021 ). The lotus seeds, rhizomes, and flowers have versatile uses, including as popular vegetable and ornamental plant with diverse medicinal properties ( Sun et al, 2020 ). Lotus is popularly cultivated in Asia, and it is mainly categorized as seed-, rhizome-, and flower-lotus based on agronomic traits and distinct uses ( Yang et al, 2015 ).…”

“…Rhizome-lotus is produced for its edible underground stems, while flower-lotus is popular for its diversely colored and shaped flowers ( Yang et al, 2015 ). TFs, including MYB, WRKY, bHLH, ERF, and bZIP have previously been reported to play crucial roles in lotus growth and development ( Chen et al, 2013 ; Deng et al, 2016 ; Li et al, 2018b ; Li et al, 2019 ; Sun et al, 2020 ). For example, Deng et al (2016) demonstrated the NnMYB5 -mediated transcriptional activation of anthocyanin synthesis, and its overexpression induced higher anthocyanin accumulation in immature transgenic Arabidopsis seeds and flower stalks.…”

Transcriptome-Wide Characterization of Alkaloids and Chlorophyll Biosynthesis in Lotus Plumule

“…Recent studies on the development of lotus seeds have mainly focused on cotyledons, the main edible seed tissue (Wang et al, 2016 ; Li et al, 2018 ; Sun et al, 2020 ). However, despite the pharmacological significance of lotus plumule, its development process remains largely unknown.…”

Studies on Lotus Genomics and the Contribution to Its Breeding

“…ADP-glucose pyrophosphorylase (AGPase) plays an important role in regulating starch biosynthesis. The evolution of AGPase genes experienced a purification selection, and NnAGPL2a and NnAGPS1a were the candidate genes related to starch content [64]. Starch branching enzyme (SBE) genes are key regulatory genes during starch synthesis, and NnSBEI and NnSBEIII were identified as related to the chain length of amylopectin in lotus [65].…”