Synthesis and regulation of auxin and abscisic acid in maize

Physiological Mechanism of EBR for Grain-Filling and Yield Formation of Tartary Buckwheat

Tartary buckwheat is characterized by its numerous inflorescences; however, the uneven distribution of resources can lead to an overload in certain areas, significantly limiting plant productivity. Plant growth regulators effectively modulate plant growth and development. This study investigated the effects of three concentrations of brassinosteroids (EBR) on the Tartary buckwheat cultivar with high seed-setting rates, specifically Chuanqiao No. 1 (CQ1), and low seed-setting rates, namely Xiqiao No. 1 (XQ1), through field experiments. The goal was to investigate how EBR regulates buckwheat grain-filling, enhancing the seed-setting rates, and to understand the physiological mechanisms behind this improvement. The results indicated that EBR treatment followed the typical "S" type growth curve of crops, resulting in an increase in the Tartary buckwheat grain-filling rate. Varieties with high seed-setting rates demonstrated a greater capacity for grain-filling. EBR was observed to regulate hormone content, enhance the photosynthetic capacity of Tartary buckwheat, and increase yield. This was accomplished by enhancing the accumulation of photosynthetic products during the grain-filling period. Specifically, EBR elevated the activity of several key enzymes, including pre-leaf sucrose phosphate synthase (SPS), seed sucrose synthase (SS), late grain-filling acid invertase (AI), grain-filling leaf SPS, and grain SS. These changes led to an increased accumulation of sucrose and starch from photosynthetic products. In summary, the G2 concentration of EBR (0.1 mg/L) demonstrated the most significant impact on the seed-setting rates and yield enhancement of Tartary buckwheat.

Diverse functional interactions between ABA and ethylene in plant development and responses to stress

Abscisic acid (ABA) and ethylene are two essential hormones that play crucial roles throughout the entire plant life cycle and in their tolerance to abiotic or biotic stress. In recent decades, increasing research has revealed that, in addition to their individual roles, these two hormones are more likely to function through their interactions, forming a complex regulatory network. More importantly, their functions change and their interactions vary from synergistic to antagonistic depending on the specific plant organ and development stage, which is less focused, compared and systematically summarized. In this review, we first introduce the general synthesis and action signaling pathways of these two plant hormones individually and their interactions in relation to seed dormancy and germination, primary root growth, shoot development, fruit ripening, leaf senescence and abscission, and stomatal movement regulation under both normal and stress conditions. A better understanding of the complex interactions between ABA and ethylene will enhance our knowledge of how plant hormones regulate development and respond to stress and may facilitate the development of crops with higher yields and greater tolerance to stressful environments through tissue-specific genetic modifications in the future.

GWAS and Meta-QTL Analysis of Kernel Quality-Related Traits in Maize

The quality of corn kernels is crucial for their nutritional value, making the enhancement of kernel quality a primary objective of contemporary corn breeding efforts. This study utilized 260 corn inbred lines as research materials and assessed three traits associated with grain quality. A genome-wide association study (GWAS) was conducted using the best linear unbiased estimator (BLUE) for quality traits, resulting in the identification of 23 significant single nucleotide polymorphisms (SNPs). Additionally, nine genes associated with grain quality traits were identified through gene function annotation and prediction. Furthermore, a total of 697 quantitative trait loci (QTL) related to quality traits were compiled from 27 documents, followed by a meta-QTL analysis that revealed 40 meta-QTL associated with these traits. Among these, 19 functional genes and reported candidate genes related to quality traits were detected. Three significant SNPs identified by GWAS were located within the intervals of these QTL, while the remaining eight significant SNPs were situated within 2 Mb of the QTL. In summary, the findings of this study provide a theoretical framework for analyzing the genetic basis of corn grain quality-related traits and for enhancing corn quality.

Complete genome sequence of potential plant growth-promoting Bacillus altitudinis strain AIMST-CREST03 isolated from paddy field bulk soil

We present the complete genome of a potential plant growth-promoting bacteria Bacillus altitudinis AIMST-CREST03 isolated from a high-yielding paddy plot. The genome is 3,669,202 bp in size with a GC content of 41%. Annotation predicted 3,327 coding sequences, including several genes required for plant growth promotion.

5'-UTR allelic variants and expression of the lycopene-ɛ-cyclase LCYE gene in maize (Zea mays L.) inbred lines of Russian selection

In breeding, biofortification is aimed at enriching the edible parts of the plant with micronutrients. Within the framework of this strategy, molecular screening of collections of various crops makes it possible to determine allelic variants of genes, new alleles, and the linkage of allelic variants with morphophysiological traits. The maize (Zea mays L.) is an important cereal and silage crop, as well as a source of the main precursor of vitamin A - β-carotene, a derivative of the β,β-branch of the carotenoid biosynthesis pathway. The parallel β,ε-branch is triggered by lycopene-ε-cyclase LCYE, a low expression of which leads to an increase in provitamin A content and is associated with the variability of the 5'-UTR gene regulatory sequence. In this study, we screened a collection of 165 maize inbred lines of Russian selection for 5'- UTR LCYE allelic variants, as well as searched for the dependence of LCYE expression levels on the 5'-UTR allelic variant in the leaves of 14 collection lines. 165 lines analyzed were divided into three groups carrying alleles A2 (64 lines), A5 (31) and A6 (70), respectively. Compared to A2, allele A5 contained two deletions (at positions -267- 260 and -296-290 from the ATG codon) and a G251→T substitution, while allele A6 contained one deletion (-290-296) and two SNPs (G251→T, G265→T). Analysis of LCYE expression in the leaf tissue of seedlings from accessions of 14 lines differing in allelic variants showed no associations of the 5'-UTR LCYE allele type with the level of gene expression. Four lines carrying alleles A2 (6178-1, 6709-2, 2289-3) and A5 (5677) had a significantly higher level of LCYE gene expression (~0.018-0.037) than the other 10 analyzed lines (~0.0001-0.004), among which all three allelic variants were present.

Comparative Coexpression Analysis of Indole Synthase and Tryptophan Synthase A Reveals the Independent Production of Auxin via the Cytosolic Free Indole

Indole synthase (INS), a homologous cytosolic enzyme of the plastidal tryptophan synthase A (TSA), has been reported as the first enzyme in the tryptophan-independent pathway of auxin synthesis. This suggestion was challenged as INS or its free indole product may interact with tryptophan synthase B (TSB) and, therefore, with the tryptophan-dependent pathway. Thus, the main aim of this research was to find out whether INS is involved in the tryptophan-dependent or independent pathway. The gene coexpression approach is widely recognized as an efficient tool to uncover functionally related genes. Coexpression data presented here were supported by both RNAseq and microarray platforms and, hence, considered reliable. Coexpression meta-analyses of Arabidopsis genome was implemented to compare between the coexpression of TSA and INS with all genes involved in the production of tryptophan via the chorismate pathway. Tryptophan synthase A was found to be coexpressed strongly with TSB1/2, anthranilate synthase A1/B1, phosphoribosyl anthranilate transferase1, as well as indole-3-glycerol phosphate synthase1. However, INS was not found to be coexpressed with any target genes suggesting that it may exclusively and independently be involved in the tryptophan-independent pathway. Additionally, annotation of examined genes as ubiquitous or differentially expressed were described and subunits-encoded genes available for the assembly of tryptophan and anthranilate synthase complex were suggested. The most probable TSB subunits expected to interact with TSA is TSB1 then TSB2. Whereas TSB3 is only used under limited hormone conditions to assemble tryptophan synthase complex, putative TSB4 is not expected to be involved in the plastidial synthesis of tryptophan in Arabidopsis.

Novel insights into maize (Zea mays) development and organogenesis for agricultural optimization

In maize, intrinsic hormone activities and sap fluxes facilitate organogenesis patterning and plant holistic development; these hormone movements should be a primary focus of developmental biology and agricultural optimization strategies. Maize (Zea mays) is an important crop plant with distinctive life history characteristics and structural features. Genetic studies have extended our knowledge of maize developmental processes, genetics, and molecular ecophysiology. In this review, the classical life cycle and life history strategies of maize are analyzed to identify spatiotemporal organogenesis properties and develop a definitive understanding of maize development. The actions of genes and hormones involved in maize organogenesis and sex determination, along with potential molecular mechanisms, are investigated, with findings suggesting central roles of auxin and cytokinins in regulating maize holistic development. Furthermore, investigation of morphological and structural characteristics of maize, particularly node ubiquity and the alternate attachment pattern of lateral organs, yields a novel regulatory model suggesting that maize organ initiation and subsequent development are derived from the stimulation and interaction of auxin and cytokinin fluxes. Propositions that hormone activities and sap flow pathways control organogenesis are thoroughly explored, and initiation and development processes of distinctive maize organs are discussed. Analysis of physiological factors driving hormone and sap movement implicates cues of whole-plant activity for hormone and sap fluxes to stimulate maize inflorescence initiation and organ identity determination. The physiological origins and biogenetic mechanisms underlying maize floral sex determination occurring at the tassel and ear spikelet are thoroughly investigated. The comprehensive outline of maize development and morphogenetic physiology developed in this review will enable farmers to optimize field management and will provide a reference for de novo crop domestication and germplasm improvement using genome editing biotechnologies, promoting agricultural optimization.

The Integration of Metabolomics and Transcriptomics Provides New Insights for the Identification of Genes Key to Auxin Synthesis at Different Growth Stages of Maize

As a staple food crop, maize is widely cultivated worldwide. Sex differentiation and kernel development are regulated by auxin, but the mechanism regulating its synthesis remains unclear. This study explored the influence of the growth stage of maize on the secondary metabolite accumulation and gene expression associated with auxin synthesis. Transcriptomics and metabonomics were used to investigate the changes in secondary metabolite accumulation and gene expression in maize leaves at the jointing, tasseling, and pollen-release stages of plant growth. In total, 1221 differentially accumulated metabolites (DAMs) and 4843 differentially expressed genes (DEGs) were screened. KEGG pathway enrichment analyses of the DEGs and DAMs revealed that plant hormone signal transduction, tryptophan metabolism, and phenylpropanoid biosynthesis were highly enriched. We summarized the key genes and regulatory effects of the tryptophan-dependent auxin biosynthesis pathways, giving new insights into this type of biosynthesis. Potential MSTRG.11063 and MSTRG.35270 and MSTRG.21978 genes in auxin synthesis pathways were obtained. A weighted gene co-expression network analysis identified five candidate genes, namely TSB (Zm00001d046676 and Zm00001d049610), IGS (Zm00001d020008), AUX2 (Zm00001d006283), TAR (Zm00001d039691), and YUC (Zm00001d025005 and Zm00001d008255), which were important in the biosynthesis of both tryptophan and auxin. This study provides new insights for understanding the regulatory mechanism of auxin synthesis in maize.

Identification of potential pathways associated with indole-3-butyric acid in citrus bud germination via transcriptomic analysis

Indole-3-butyric acid (IBA) is widely used to encourage root development in cuttings of general field crops, vegetables, forest trees, fruit trees, and flowers. However, previous studies reported that IBA inhibited the germination of citrus buds via an unknown molecular mechanism. This study aimed to unravel the regulatory mechanisms underlying this inhibition. Citrus apical buds were sprayed with 100 mg ⋅ L^-1 IBA. Subsequently, the plant hormone levels were analyzed, and transcriptomic analysis was performed. The results identified 3325 upregulated genes and 2926 downregulated genes in the citrus apical buds. The gene set enrichment analysis method was used to determine the Gene Ontology related to the treatment. Genes were enriched into 157 sets, including 17 upregulated sets and 140 downregulated sets, after indole butyric acid treatment. The upregulated gene sets were related to glucose import, sugar transmembrane transporter activity, and photosynthesis. The downregulated genes were mainly related to the ribosomal subunit and cell cycle process under butyric acid treatment. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed the enrichment of 11 pathways. Of note, genes related to the ribosome and proteasome pathways were significantly downregulated. Only one pathway was significantly upregulated: the autophagy pathway. Overall, these results provided insights into the molecular mechanisms underpinning the IBA-mediated inhibition of citrus bud germination inhibition. Also, the study provided a large transcriptomics dataset that could be used for further research.