Over-Expression of Phosphoserine Aminotransferase-Encoding Gene (AtPSAT1) Prompts Starch Accumulation in L. turionifera under Nitrogen Starvation

Abstract

It has been demonstrated that the phosphorylation pathway of L-serine (Ser) biosynthesis (PPSB) is very important in plant growth and development, but whether and how PPSB affects nitrogen metabolism and starch accumulation has not been fully elucidated. In this study, we took the energy plant duckweed (strain Lemna turionifera 5511) as the research object and used a stable genetic transformation system to heterologously over-expressing Arabidopsis AtPSAT1 (the gene encoding phosphoserine aminotransferase, the second enzyme of PPSB). Our results showed that, under nitrogen starvation, the transgenic plants grew faster, with higher values of Fv/Fm, rETR, and Y(II), as well as fresh and dry weight, than the wild-type. More promisingly, the accumulation of starch was also found to be significantly improved when over-expressing AtPSAT1 in the transgenic plants. qRT-PCR analysis results showed that the expression of genes related to nitrogen assimilation, carbon metabolism, and starch biosynthesis was up-regulated, while the expression of starch degradation-related genes was down-regulated by AtPSAT1 over-expression. We propose that the increased starch accumulation caused by AtPSAT1 over-expression may result from both elevated photosynthetic capacity and nitrogen utilization efficiency. This research sheds new light on the mechanism underlying the ability of PPSB to coordinate nitrogen and carbon metabolism, and provides a feasible way to improve starch production, that is, through engineering PPSB in crops.

Overexpression of Phosphoserine Aminotransferase (PSAT)-Enhanced Cadmium Resistance and Accumulation in Duckweed (Lemna turionifera 5511)

“…This research suggests that the movement of the gate-keeping loop (residues 391–401) is a key element in regulating the catalytic activity of PSAT when 3-PHP binds to P-Ser. Overexpression of PSAT 1 in duckweed ( Lemna turionifera 5511) increases starch production by promoting light and nitrogen utilization [ 15 ]. Our investigation into PSAT ’s transcriptomic response to Cd stress revealed the downregulation of most genes in glycolysis and the TCA cycle, potentially resulting from biochemical reactions triggered by stress-induced injury.…”

“…Serine serves as a precursor for tryptophan, glycine, and cysteine, which are essential for nucleic acid and protein biosynthesis [ 14 ]. Furthermore, PSAT has been identified as a driver of starch accumulation in duckweed under nitrogen-starved conditions [ 15 ]. In our previous study, significant upregulation in the expression of both PSAT and GDH was observed during Cd stress [ 2 ].…”

Shoot transcriptome revealed widespread differential expression and potential molecular mechanisms of chickpea (Cicer arietinum L.) against Fusarium wilt

“…In the present study, genes related to NAD (P)H, such as NADH-dependent glutamate synthase, NAD(P)H-quinone oxidoreductase subunit 4, NADH dehydrogenase (ubiquinone) Fe-S protein, NADH:quinone reductase, and NADHubiquinone oxidoreductase, showed significant up-regulation in resistant genotypes, confirming its role in energy homeostasis in plants under stress conditions. Other than NADH-related genes, shoot transcriptome data of resistant genotypes in the present study also showed significant up-regulation of other genes involved in energy metabolism, such as phosphoenolpyruvate carboxylase (Wang et al, 2016;Waseem and Ahmad, 2019), alcohol dehydrogenase (Su et al, 2020), alanine transaminase (Bashar et al, 2020), ATP citrate (pro-S)-lyase (Liu F. et al, 2022), ATPase , carbonic anhydrase (Rudenko et al, 2021), cytochrome c, cytochrome c oxidase (Guerra-Castellano et al, 2018;Analin et al, 2020), fructose-bisphosphate aldolase (Lv et al, 2017;Cai et al, 2022), malate dehydrogenase (Song et al, 2022), 6-phosphofructokinase 1 (Wang H. et al, 2021), photosystem II P680 reaction center D1 protein (Landi and Guidi, 2022), phosphoserine aminotransferase (Wang et al, 2022), pyruvate-orthophosphate dikinase (Yadav et al, 2020), and serine O-acetyltransferase (Mulet et al, 2004;Liu D. et al, 2022), and their molecular mechanism and role in energy homeostasis in different crops is well reviewed. It indicates that the significant up-regulation of the genes involved in energy metabolism in KWR 108 might have helped it to cope with Fusarium wilt stress by maintaining energy homeostasis in cells under stress conditions.…”