Ling Jiang

Methionine is an essential amino acid that initiates protein synthesis and serves as a substrate for various chemical reactions. Methionine metabolism plays an important role in Arabidopsis seed germination, but how methionine works in seed germination of maize has not been elucidated. We compared the changes in germination rate, the contents of methionine and folates, and transcriptional levels using transcriptome analysis under water or exogenous methionine treatment. The results indicate that the application of methionine increases seed germination rate (95% versus 70%), leading to significant differences in the content of methionine at 36 h, which brought the rapid increase forward by 12 h in the embryo and endosperm. Transcriptome analysis shows that methionine mainly affects the proliferation and differentiation of cells in the embryo, and the degradation of storage substances and signal transduction in the endosperm. In particular, multiple phenylpropanoid biosynthetic genes were triggered upon methionine treatment during germination. These results provide a theoretical foundation for promoting maize seed germination and serve as a valuable theoretical resource for seed priming strategies.

(1) Background: Salt stress is an abiotic factor that limits maize yield and quality. A highly salt-tolerance inbred AS5 and a salt-sensitive inbred NX420 collected from Ningxia Province, China, were used to identify new genes for modulating salt resistance in maize. (2) Methods: To understand the different molecular bases of salt tolerance in AS5 and NX420, we performed BSA-seq using an F2 population for two extreme bulks derived from the cross between AS5 and NX420. Transcriptomic analysis was also conducted for AS5 and NX420 at the seedling stage after treatment with 150 mM of NaCl for 14 days. (3) Results: AS5 had a higher biomass and lower Na⁺ content than NX420 in the seedling stage after treatment with 150 mM NaCl for 14 days. One hundred and six candidate regions for salt tolerance were mapped on all of the chromosomes through BSA-seq using F2 in an extreme population. Based on the polymorphisms identified between both parents, we detected 77 genes. A large number of differentially expressed genes (DEGs) at the seedling stage under salt stress between these two inbred lines were detected using transcriptome sequencing. GO analysis indicated that 925 and 686 genes were significantly enriched in the integral component of the membrane of AS5 and NX420, respectively. Among these results, two and four DEGs were identified as overlapping in these two inbred lines using BSA-seq and transcriptomic analysis, respectively. Two genes (Zm00001d053925 and Zm00001d037181) were detected in both AS5 and NX420; the transcription level of Zm00001d053925 was induced to be significantly higher in AS5 than in NX420 (41.99 times versus 6.06 times after 150 mM of NaCl treatment for 48 h), while the expression of Zm00001d037181 showed no significant difference upon salt treatment in both lines. The functional annotation of the new candidate genes showed that it was an unknown function protein. (4) Conclusions: Zm00001d053925 is a new functional gene responding to salt stress in the seedling stage, which provides an important genetic resource for salt-tolerant maize breeding.

Vitamin B and its derivatives possess diverse physiological functions and are essential micronutrients for humans. Their variation in crops is important for the identification of genetic resources used to develop new varieties with enhanced vitamin B. In this research, remarkable variations were observed in kernels of 156 maize inbred lines, ranging from 107.61 to 2654.54 μg per 100 g for vitamin B1, 1.19–37.37 μg per 100 g for B2, 19.60–213.75 μg per 100 g for B3, 43.47–590.86 μg per 100 g for B5, and 138.59–1065.11 μg per 100 g for B6. Growing inbreeds in Hainan and Hebei provinces of China revealed environmental and genotype interactions among these vitamins and the correlations between them in maize grain. Several inbred lines were identified as good sources of vitamin B and promising germplasms for maize breeding, namely By855 and Si273 are overall rich in all the studied vitamins, and GY386B and CML118 are specially enriched with derivatives of vitamin B6. The present study can assist maize breeders with germplasm resources of vitamin B for biofortification to offer people nutritious foods.

Previously, the complexity of folate accumulation in the early stages of maize kernel development has been reported, but the mechanisms of folate accumulation are unclear. Two maize inbred lines, DAN3130 and JI63, with different patterns of folate accumulation and different total folate contents in mature kernels were used to investigate the transcriptional regulation of folate metabolism during late stages of kernel formation by comparative transcriptome analysis. The folate accumulation during DAP 24 to mature kernels could be controlled by circumjacent pathways of folate biosynthesis, such as pyruvate metabolism, glutamate metabolism, and serine/glycine metabolism. In addition, the folate variation between these two inbred lines was related to those genes among folate metabolism, such as genes in the pteridine branch, para-aminobenzoate branch, serine/tetrahydrofolate (THF)/5-methyltetrahydrofolate cycle, and the conversion of THF monoglutamate to THF polyglutamate. The findings provided insight into folate accumulation mechanisms during maize kernel formation to promote folate biofortification.

As the fourth largest staple crop in China, potatoes are a significant source of food and revenue, and provide diverse vitamins to human. However, the variation of vitamin retention in tubers after cooking were seldom evaluated. In this study, we evaluated the effects of steaming on water-soluble vitamins (vitamin B9 and vitamin C) and liposoluble vitamin (vitamin E) in tubers from eight potato cultivars grown in northern China. We found that these cultivars contained wide ranges of vitamin B9 (8.60–19.93 μg/100 g FW), vitamin C (46.67–155.44 mg/100 g FW), and vitamin E (15.34–33.82 mg/kg FW), with the highest vitamins B9, C, and E content in cultivars V7, XinDaPing, and QingShu 9, respectively. After steaming, vitamin contents decreased in most cultivars; levels of these three vitamins in tubers of cultivars ‘Tianshu11’ and ‘XinDaPing’ were higher than others, indicating that these two cultivars could be better sources among the detected ones for multiple vitamins after steaming.

Folate deficiency is a global health problem. Biofortification has been considered a cost-effective means to tackle this problem. Here, we describe the genetic cloning and functional identification of a previously uncharacterised plant protein, designated as CTM, which functions as an enzyme in folate metabolism. Plant CTMs are capable of catalysing 5-methyl-tetrahydrofolate to MeFox, a pyrazino-s-triazine derivative of 4α-hydroxy-5-methyl-tetrahydrofolate. The natural asparagine-to-glycine substitution caused by an A-to-G single nucleotide variation in maize CTM enhances its enzymatic activity, as demonstrated by in vitro enzymatic assays and in silico analyses using a maize CTM structure model based on a monomeric sorghum CTM crystal. Loss of the CTM function led to accumulation of 5-methyl-tetrahydrofolate, and overexpression of the maize CTM carrying the G-allele boosted the metabolic flow towards MeFox, and showed no negative impacts on plant growth. Our results suggest that CTM, which has evolved 5-methyl-tetrahydrofolate-to-MeFox converting activity in plants, could be valuable for developing folate-biofortified crops to provide an alternative to the challenge presented by the global folate deficiency.