Nitrogen topdressing timing modifies free amino acids profiles and storage protein gene expression in wheat grain

Abstract

BackgroundNitrogen is one basic element of amino acids and grain protein in wheat. In field experiments, wheat plants were subjected to different timing of nitrogen topdressing treatments: at the stages of emergence of the top fifth leaf (TL5), top third leaf (TL3) and top first leaf (TL1) to test the regulatory effects of nitrogen topdressing timing on grain protein quality. The underlying mechanisms were elucidated by clarifying the relationship between proteolysis in vegetative organs and accumulation of amino acids in the endosperm cavity, conversion of amino acids, and storage protein synthesis in endosperm of wheat grain.ResultsDelayed nitrogen topdressing up-regulated gene expression related to nitrogen metabolism and protease synthesis in the flag leaf, followed by more free amino acids being transported to both the cavity and the endosperm from 7 days after anthesis (DAA) to 13 DAA in TL1. TL1 enhanced the conversion between free amino acids in endosperm and upregulated the expression of genes encoding high molecular weight (HMW) and low molecular weight (LMW) subunits and protein disulfide isomerases-like (PDIL) proteins, indicating that the synthesis and folding of glutenin were enhanched by delayed nitrogen topdressing. As a consequense, the content of glutenin macropolymers (GMP) and glutenin increased with delaying nitrogen topdressing.ConclusionsThe results highlight the relationship between nitrogen remobilization and final grain protein production and suggest that the nitrogen remobilization processes could be a potential target for improving the quality of wheat grain. Additionally, specific gene expression related to nitrogen topdressing was identified, which conferred more detailed insights into underlying mechanism on the modification protein quality.Electronic supplementary materialThe online version of this article (10.1186/s12870-018-1563-3) contains supplementary material, which is available to authorized users.

Absence of Dx2 at Glu-D1 Locus Weakens Gluten Quality Potentially Regulated by Expression of Nitrogen Metabolism Enzymes and Glutenin-Related Genes in Wheat

“…Overexpression of the AlaAT gene significantly increases the grain nitrogen use efficiency [16]. Higher expression levels of cysteine and thiol proteases indicate the strong degradation and mobilization of soluble proteins in the leaves [11]. In the present study, the expression levels of TaGS (TaGS1 and TaGS2) and TaAlaAT were higher in HMW-D1p than HMW-D1a, and this was also the case for the genes encoding cysteine and thiol proteases ( Figure 6).…”

“…PPIase facilitates the accumulation of protein polymers with the assistance of SUMO1 [21]. The expression of PDI catalyzes the formation of disulfide bonds, which are positively correlated with protein polymer formation [11,22]. In the present study, the expression levels of TaPPIase, TaSUMO1, and TaPDIL2-1 were higher in HMW-D1p than HMW-D1a ( Figure 7E-G), and the maximum TaPDIL2-1 expression level occurred earlier in HMW-D1p, thereby suggesting that larger protein polymers were formed in HMW-D1p, as demonstrated by the accumulation of PBs and GMP, and the concentration of disulfide bonds ( Figure 1A, Figure 2E, and Figure 3).…”

“…HMW-GS genes are specifically expressed in the endosperm and they have similar expression patterns [10,11]. Regulation of the expression of HMW-GS occurs primarily at the transcriptional level, where it involves cis-acting motifs in the HMW-GS promoters and trans-acting transcription factors (TFs) [4].…”

“…Protein disulfide isomerase (PDI) catalyzes the formation of disulfide bonds, which are regarded as the determinant bridges during protein polymerization [22]. The high level expression of genes encoding PPIase, SUMO1, and PDI enhances the folding of storage proteins during grain-filling, thereby leading to the accumulation of more glutenin macropolymers (GMPs) [11,21,23]. HMW-GSs contribute to glutenin polymerization via intra-/intermolecular disulfide bonds and hydrogen bonds [4], and the effects of single HMW-GSs on glutenin polymerization have been reported [8].…”

Optimized Nitrogen Topdressing Strategies Enhance Steviol Glycoside Productivity in Stevia (Stevia rebaudiana Bertoni) Plants

“…Cui et al (2010) demonstrated the achievability of maximized wheat yield and minimized environmental risks through the adjustment of the N fertilization proportions between seasons. Likewise, others also successfully improved crop yield, NUE, and grain quality by integrating the N fertilization amount and topdressing timing (Liu et al 2019b;Qu et al 2018;Zhong et al 2018). In other plants rather than food crops, the benefits of topdressing or controlreleased N fertilization on plant growth and productivity have been similarly reported in Platycodon grandiflorum (Zhu and Zhang 2017), Cleome gynandra (Mavengahama 2013), and Glycine max (Zhou et al 2019a).…”