Unveiling the Regulatory Role of miRNAs in Internode Elongation: Integrated Analysis of MicroRNA and mRNA Expression Profiles across Diverse Dwarfing Treatments in Maize (Zea mays L.).

MicroRNAs are crucial regulators of gene expression in maize. However, the mechanisms through which miRNAs control internode elongation remain poorly understood. This study engineered varying levels of internode elongation inhibition, revealing that dwarfing treatments diminished gibberellin levels, curtailed cell longitudinal growth, and slowed the rate of internode elongation. Comprehensive transcriptome and miRNA profiling of the internode elongation zone showed gene expression changes that paralleled the extent of the internode length reduction. We identified 543 genes and 29 miRNAs with significant correlations to internode length, predominantly within families, including miR164 and miR396. By incorporating target gene expression levels, we pinpointed nine miRNA-mRNA pairs that are significantly associated with the regulation of the internode elongation. The inhibitory effects of these miRNAs on their target genes were confirmed through dual-luciferase reporter assays. Overexpression of miR164h in maize resulted in increased internode and cell length, suggesting a novel genetic avenue for manipulating plant stature. These miRNAs may also serve as precise spatiotemporal regulators for in vitro plant development.

A novel ABA functional analogue B2 enhances drought tolerance in wheat.

Drought stress negatively affects wheat growth and yield. Application of drought agent is an effective way to improve crop drought tolerance, therefore increasing crop yield. Based on the structure of abscisic acid (ABA), Pyrabactin and coronatine (COR), we designed the target compound B2. To investigate the function of B2 in alleviating drought stress on wheat, the drought-resistant variety ND212 and drought-sensitive variety LX99 were used under hydroponic conditions. The results showed that B2 had a similar function with ABA, especially 0.01 µmol·L-1 B2. Under drought stress conditions, 0.01 µmol·L-1 B2 increased the water content of wheat, enhanced the osmotic adjustment ability of leaves, and reduced the toxicity of reactive oxygen species on cells. What's more, 0.01 µmol·L-1 B2 improved the expression level of ABA-responsive genes TaSnRK2.4 and TaMYB3R1. It also improved the expression level of drought-responsive genes TaSRHP and TaERF3. Taken together, B2 enhanced drought tolerance in wheat by activating ABA signaling pathway.

System Analysis of MIRNAs in Maize Internode Elongation.

MicroRNAs (miRNAs), the post-transcriptional gene regulators, are known to play an important role in plant development. The identification of differentially expressed miRNAs could better help us understand the post-transcriptional regulation that occurs during maize internode elongation. Accordingly, we compared the expression of MIRNAs between fixed internode and elongation internode samples and classified six differentially expressed MIRNAs as internode elongation-responsive miRNAs including zma-MIR160c, zma-MIR164b, zma-MIR164c, zma-MIR168a, zma-MIR396f, and zma-MIR398b, which target mRNAs supported by transcriptome sequencing. Functional enrichment analysis for predictive target genes showed that these miRNAs were involved in the development of internode elongation by regulating the genes respond to hormone signaling. To further reveal how miRNA affects internode elongation by affecting target genes, the miRNA-mRNA-PPI (protein and protein interaction) network was constructed to summarize the interaction of miRNAs and these target genes. Our results indicate that miRNAs regulate internode elongation in maize by targeting genes related to cell expansion, cell wall synthesis, transcription, and regulatory factors.

Coronatine enhances drought tolerance in winter wheat by maintaining high photosynthetic performance.

Coronatine (COR) is a phytotoxin produced by Pseudomonas syringae. Its structure is similar to those of jasmonates (JAs), which play diverse roles in multiple plant biotic and abiotic defenses. However, the biological activity of COR is 1000 times greater than the activity of JA. In addition to being involved in the JA pathway, COR affects plant photosynthetic efficiency. In this study, we examined wheat blade pretreatment with COR. Blades treated with COR remained green longer than those of control plants under drought stress conditions, resulting in less yield loss with COR treatment. To investigate the mechanism of COR in drought resistance further, we employed two-dimensional gel electrophoresis technology and matrix-assisted laser desorption/ionization mass spectrometry to sequester and identify key proteins. Six COR-inducible proteins that are located in the chloroplast and involved directly in photosynthesis were found. The wheat homologue of protein gi|326509937 is degradation of periplasmic proteins 1 (DEGP1) in Arabidopsis, which is a response to photosystem II reparation, and was maintained at a low level with COR treatment. Finally, we measured levels of chlorophyll and photosynthetic performance to reveal the phenotypic effect of COR. Taken together, the results demonstrate that COR enhances drought tolerance by maintaining high photosynthetic performance.