SH1-dependent maize seed development and starch synthesis via modulating carbohydrate flow and osmotic potential balance

Abstract

Background As the main form of photoassimilates transported from vegetative tissues to the reproductive organs, sucrose and its degradation products are crucial for cell fate determination and development of maize kernels. Despite the relevance of sucrose synthase SH1 (shrunken 1)-mediated release of hexoses for kernel development, the underlying physiological and molecular mechanisms are not yet well understood in maize (Zea mays). Results Here, we identified a new allelic mutant of SH1 generated by EMS mutagenesis, designated as sh1*. The mutation of SH1 caused more than 90% loss of sucrose synthase activity in sh1* endosperm, which resulted in a significant reduction in starch contents while a dramatic increase in soluble sugars. As a result, an extremely high osmolality in endosperm cells of sh1* was generated, which caused kernel swelling and affected the seed development. Quantitative measurement of phosphorylated sugars showed that Glc-1-P in endosperm of sh1* (17 μg g− 1 FW) was only 5.2% of that of wild-type (326 μg g− 1 FW). As a direct source of starch synthesis, the decrease of Glc-1-P may cause a significant reduction in carbohydrates that flow to starch synthesis, ultimately contributing to the defects in starch granule development and reduction of starch content. Conclusions Our results demonstrated that SH1-mediated sucrose degradation is critical for maize kernel development and starch synthesis by regulating the flow of carbohydrates and maintaining the balance of osmotic potential.

A Novel Banana Mutant “RF 1” (Musa spp. ABB, Pisang Awak Subgroup) for Improved Agronomic Traits and Enhanced Cold Tolerance and Disease Resistance

“…In this respect, ethyl methanesulfonate (EMS) is one of the most effective, reliable, and powerful mutagens; treating plants with EMS could destroy their nuclear DNA and randomly induce new mutations in the process of DNA repair (Greene et al, 2003;Jain, 2010). Creating new germplasm through EMS has been implemented for many crops, such as barley (Caldwell et al, 2004), rapeseed (Lee et al, 2018), potato (Moon et al, 2018), rice (Serrat et al, 2014), wheat (Wang et al, 2018), maize (Zhang et al, 2020a), and Chinese cabbage (Lu et al, 2016). Notably, Jankowicz-Cieslak et al (2012) treated the meristem of banana stem tips with EMS and obtained high-density GC-AT base pair transition mutations, which demonstrated the high efficiency of EMS in banana germplasm innovation.…”

Characterization and Transcriptome Analysis of Maize Small-Kernel Mutant smk7a in Different Development Stages

“…In our RNA-seq results, almost all of the DEGs involved in this sucrose metabolism process exhibited a decreased expression level in smk7a , including the well-known genes SH1 , SH2 , and BT2 . SH1 encodes sucrose synthase, and the loss of the function of SH1 caused a significant reduction in the carbohydrates that flow to starch synthesis, ultimately contributing to the defects in the starch granule development and reduction of the starch content [ 46 ]. SH2 and BT2 encode AGPase and are rate-limiting enzymes in starch biosynthesis.…”

Exploring the Developmental Progression of Endosperm Cavity Formation in Maize Grain and the Underlying Molecular Basis Using X-Ray Tomography and Genome Wide Association Study

“…In this context, we hypothesize that the reduction of Zm00001d013173 may disrupt the sugar–lectin equilibrium, leading to more sugar release from the sugar–lectin complex, which in turn, results in the disruption of sugar homeostasis or osmotic balance, subsequently cell death and the formation EC. Indeed, an increase in sugar content and osmotic potential in the maize endosperm results in the formation of EC, as a result of the silencing of SH1 ( Zhang et al, 2020 ). On another hand, a previous study suggested that a strawberry homolog of Zm00001d013173, CBMFaEXP2, played a role in modifying and loosening plant cell wall structure ( Nardi et al, 2015 ).…”