Low temperature is a limiting factor of seed germination and plant growth. Although there is a lot information on the response of maize to low temperatures, there is still poorly description of how histone methylation affects maize germination and growth development at low temperatures. In this study, the germination rate and physiological indexes of wild-type maize inbred lines B73 (WT), SDG102 silencing lines (AS), SDG102 overexpressed lines (OE) at germination stage and seedling stage were measured under low temperature stress (4 ℃), and transcriptome sequencing was applied to analyze the differences of gene expression in panicle leaves among different materials. The results showed that the germination rate of WT and OE maize seeds at 4 ℃ was significantly lower than 25 ℃. The content of MDA, SOD and POD of 4 ℃ seeding leaves higher than contrast. Transcriptome sequencing results showed that there were 409 different expression genes (DEGs) between WT and AS, and the DEGs were mainly up-regulated expression in starch and sucrose metabolism and phenylpropanoid biosynthesis. There were 887 DEGs between WT and OE, which were mainly up-regulated in the pathways of plant hormone signal transduction, porphyrin and chlorophyll metabolism. This result could provide a theoretical basis for analyzing the growth and development of maize from the perspective of histone methylation modification.

Salt stress is an important environmental factor affecting crop growth and development. One of the important ways to improve the salt tolerance of rice is to identify new salt-tolerance genes, reveal possible mechanisms, and apply them to the creation of new germplasm and the breeding of new varieties. In this study, the salt-sensitive japonica variety Tong 35 (T35) and salt-tolerant japonica variety Ji Nongda 709 (JND709) were used. Salt stress treatment with a 150 mmol/L NaCl solution (the control group was tested without salt stress treatment simultaneously) was continued until the test material was collected after the rice germination period. Twelve cDNA libraries were constructed, and 5 comparator groups were established for transcriptome sequencing. On average, 9.57G of raw sequencing data were generated per sample, with alignment to the reference genome above 96.88% and alignment to guanine-cytosine (GC) content above 53.86%. A total of 16,829 differentially expressed genes were present in the five comparison groups, of which 2390 genes were specifically expressed in T35 (category 1), 3306 genes were specifically expressed in JND709 (category 2), and 1708 genes were differentially expressed in both breeds (category 3). Differentially expressed genes were subjected to gene ontology (GO), functional enrichment analysis, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, which revealed that these genes belonged to three main classes: molecular function, cellular components, and biological processes. KEGG pathway analysis showed that the significantly enriched pathways for these differentially expressed genes included phenylpropane biosynthesis, phytohormone signaling, and the interaction of plants with pathogens. In this study, we provided a reference for studying the molecular mechanism underlying salt tolerance during germination.

Salt stress has become a major limiting factor of rice (Oryza sativa L.) yield worldwide. Appropriate nitrogen application contributes to improvement in the salt tolerance of rice. Here, we show that improvement in nitrogen-use efficiency increases salt stress tolerance in rice. Rice varieties with different nitrogen-use efficiencies were subjected to salt stress; they were stimulated with 50, 100, and 150 mmol/L of NaCl solution at the seedling stage and subjected to salinities of 0.2, 0.4%, and 0.6% at the reproductive growth stage. Compared with nitrogen-inefficient rice varieties, the nitrogen-efficient rice varieties showed significant increases in the expression levels of nitrogen-use-efficiency-related genes (TOND1 and OsNPF6.1), nitrogen content (5.1–12.1%), and nitrogen-use enzyme activities (11.7–36.4%) when under salt stress conditions. The nitrogen-efficient rice varieties showed a better adaptation to salt stress, as shown by the decrease in leaf-withering rate (4.7–10.3%), the higher chlorophyll (3.8–9.7%) and water contents (1.1–9.2%), and the better root status (7.3–9.1%) found in the rice seedlings under salt stress conditions. Analysis of physiological indexes revealed that the nitrogen-efficient rice varieties accumulated higher osmotic adjustment substances (9.7–79.9%), lower ROS (23.1–190.8%) and Na⁺ (15.9–97.5%) contents, higher expression levels of salt stress-related genes in rice seedlings under salt stress conditions. Furthermore, the nitrogen-efficient rice varieties showed higher yield under salt stress, as shown by a lower salt-induced decrease in 1000-grain weight (2.1–6.2%), harvest index (1.4–4.9%), and grain yield (2.8–4.1%) at the reproductive growth stage in salinized soil. Conversely, the nitrogen-efficient rice varieties showed better growth and physiological metabolism statuses under severe salt stress conditions. Our results suggest that nitrogen-efficient rice varieties could improve nitrogen-use and transport efficiency; accordingly, their use can improve the gene expression network, alleviating salt damage and improving grain yield under severe salt stress conditions.

Background: Low-temperature stress represents a significant constraint on rice production, especially during the germination stage. Consequently, comprehending the mechanisms underlying cold tolerance is of utmost importance for the breeding of resilient rice varieties. This research systematically examined the phenotypic and physiological responses of a cold-tolerant cultivar (JND815) and a cold-sensitive cultivar (Jiyu Japonica) to low-temperature stress (15 °C) during the germination process. Methods: Following a 17-day incubation period, physiological analyses were conducted. Transcriptomic analysis was performed to identify differentially expressed genes (DEGs), which were further subjected to KEGG enrichment analysis and Gene Ontology (GO) annotation. Additionally, the expression trends of selected cold-responsive DEGs were verified via qRT-PCR. Results: Following a 17-day incubation period, physiological analyses indicated that, in comparison to the control group (28 °C), the stress treatment notably reduced the activities of superoxide dismutase (SOD) and catalase (CAT), while increasing the activity of peroxidase (POD) and the content of malondialdehyde (MDA). Significantly, JND815 accumulated a substantially lower amount of MDA than Jiyu Japonica, suggesting superior membrane stability and oxidative stress tolerance. Transcriptomic analysis identified 11,234 and 14,164 differentially expressed genes (DEGs) in JND815 and Jiyu Japonica, respectively. KEGG enrichment analysis demonstrated that these DEGs were significantly associated with phenylpropanoid biosynthesis and carbon metabolism, and Gene Ontology (GO) annotation classified them into biological processes, cellular components, and molecular functions. The expression trends of six cold-responsive DEGs were verified by qRT-PCR to be consistent with the transcriptomic data. Conclusions: These findings offer insights into the molecular mechanisms of the low-temperature response during rice germination and lay a foundation for the genetic improvement of cold-tolerant rice varieties.

DNA methylation is an important epigenetic regulatory mechanism, it regulates gene expression by recruiting proteins involved in gene repression or by inhibiting the binding of transcription factor(s) to DNA. In this study, a novel methyltransferase 2a gene (Zmet2a) was cloned in maize and identified by polymerase chain reaction-base (PCR-base) using a bioinformatics strategy. The Zmet2a cDNA sequence is 2739 bp long and translates to 912 amino acid peptides. The Zmet2a protein revealed that it contains BAH and CHROMO structural domains, is a non-transmembrane protein that is hydrophilically unstable, and has no signal peptide structure. Meanwhile, we verified the biological roles of Zmet2a using transgenic Arabidopsis overexpressing Zmet2a and Zmet2a-knockout maize. Transgenic Zmet2a Arabidopsis thaliana showed highly significant advancement in flowering time, and Zmet2a-knockout maize showed advancement in flowering time, with significant changes in several traits. Altogether, these report the role of Zmet2a in the regulation of flowering time, which will lay a foundation for revealing the biological function and epigenetic regulation mechanism of Zmet2a in the growth, development and flowering of maize.