CHITINASE LIKE1 Regulates Root Development of Dark-Grown Seedlings by Modulating Ethylene Biosynthesis in Arabidopsis thaliana

Insights on Phytohormonal Crosstalk in Plant Response to Nitrogen Stress: A Focus on Plant Root Growth and Development

Nitrogen (N) is a vital mineral component that can restrict the growth and development of plants if supplied inappropriately. In order to benefit their growth and development, plants have complex physiological and structural responses to changes in their nitrogen supply. As higher plants have multiple organs with varying functions and nutritional requirements, they coordinate their responses at the whole-plant level based on local and long-distance signaling pathways. It has been suggested that phytohormones are signaling substances in such pathways. The nitrogen signaling pathway is closely associated with phytohormones such as auxin (AUX), abscisic acid (ABA), cytokinins (CKs), ethylene (ETH), brassinosteroid (BR), strigolactones (SLs), jasmonic acid (JA), and salicylic acid (SA). Recent research has shed light on how nitrogen and phytohormones interact to modulate physiology and morphology. This review provides a summary of the research on how phytohormone signaling affects root system architecture (RSA) in response to nitrogen availability. Overall, this review contributes to identifying recent developments in the interaction between phytohormones and N, as well as serving as a foundation for further study.

OsUGE3-mediated cell wall polysaccharides accumulation improves biomass production, mechanical strength, and salt tolerance

Cell walls constitute the majority of plant biomass and are essential for plant resistance to environmental stresses. It is promising to improve both plant biomass production and stress resistance simultaneously by genetic modification of cell walls. Here, we report the functions of a UDP-galactose/glucose epimerase 3 (OsUGE3) in rice growth and salt tolerance by characterizing its overexpressing plants (OsUGE3-OX) and loss-of-function mutants (uge3). The OsUGE3-OX plants showed improvements in biomass production and mechanical strength, whereas uge3 mutants displayed growth defects. The OsUGE3 exhibits UDP-galactose/glucose epimerase activity that provides substrates for polysaccharides polymerization, consistent with the increased biosynthesis of cellulose and hemicelluloses and strengthened walls in OsUGE3-OX plants. Notably, the OsUGE3 is ubiquitously expressed and induced by salt treatment. The uge3 mutants were hypersensitive to salt and osmotic stresses, whereas the OsUGE3-OX plants showed improved tolerance to salt and osmotic stresses. Moreover, OsUGE3 overexpression improves the homeostasis of Na⁺ and K⁺ and induces a higher accumulation of hemicelluloses and soluble sugars during salt stress. Our results suggest that OsUGE3 improves biomass production, mechanical strength, and salt stress tolerance by reinforcement of cell walls with polysaccharides and it could be targeted for genetic modification to improve rice growth under salt stress.

Building an extensible cell wall

This article recounts, from my perspective of four decades in this field, evolving paradigms of primary cell wall structure and the mechanism of surface enlargement of growing cell walls. Updates of the structures, physical interactions, and roles of cellulose, xyloglucan, and pectins are presented. This leads to an example of how a conceptual depiction of wall structure can be translated into an explicit quantitative model based on molecular dynamics methods. Comparison of the model's mechanical behavior with experimental results provides insights into the molecular basis of complex mechanical behaviors of primary cell wall and uncovers the dominant role of cellulose-cellulose interactions in forming a strong yet extensible network.

Genome-Wide Identification and Expression Analysis of Chitinase-like Genes in Petunia axillaris

Chitinase (EC 3.2.1.14) is a kind of chitin-degrading glycosidase, which plays important roles in the abiotic and biotic defense of plants. In this study, we conducted whole-genome annotation, molecular evolution, and gene expression analyses on the chitinase-like (CTL) gene family members of Petunia axillaris. Thirty-three Petunia axillarischitinase-like genes (PaCTLs) were identified from the latest Petunia genome database. According to the phylogenetic analyses, these genes were divided into GH18 and GH19 subgroups and further subdivided into five classes (Class I to Class V). Conserved motif arrangements indicated their functional relevance within each group. The expansion and homeology analyses showed that gene replication events played an important role in the evolution of PaCTLs and the increase of the GH18 subgroup members was the main reason for the expansion of the PaCTL gene family in the evolution progress. By qRT-PCR analysis, we found that most of the PaCTLs showed a very low expression level in the normal growing plants. But lots of PaCTLs showed upregulated expression profiles when the plants suffered different abiotic stress conditions. Among them, five PaCTLs responded to high temperature and exhibited significantly upregulate expression level. Correspondingly, many hormone responses, as well as biotic and abiotic stress elements were found in the promoters of PaCTLs by using cis-acting element analysis. These results provide a foundation for the exploration of PaCTLs' function and enrich the evolutionary process of the CTL gene family.

Dark-Induced Hormonal Regulation of Plant Growth and Development

The sessile nature of plants has made them extremely sensitive and flexible toward the constant flux of the surrounding environment, particularly light and dark. The light is perceived as a signal by specific receptors which further transduce the information through the signaling intermediates and effector proteins to modulate gene expression. Signal transduction induces changes in hormone levels that alters developmental, physiological and morphological processes. Importance of light for plants growth is well recognized, but a holistic understanding of key molecular and physiological changes governing plants development under dark is awaited. Here, we describe how darkness acts as a signal causing alteration in hormone levels and subsequent modulation of the gene regulatory network throughout plant life. The emphasis of this review is on dark mediated changes in plant hormones, regulation of signaling complex COP/DET/FUS and the transcription factors PIFs which affects developmental events such as apical hook development, elongated hypocotyls, photoperiodic flowering, shortened roots, and plastid development. Furthermore, the role of darkness in shade avoidance and senescence is discussed.

Mapping a Partial Andromonoecy Locus in Citrullus lanatus Using BSA-Seq and GWAS Approaches

The sexual expression of watermelon plants is the result of the distribution and occurrence of male, female, bisexual and hermaphrodite flowers on the main and secondary stems. Plants can be monoecious (producing male and female flowers), andromonoecious (producing male and hermaphrodite flowers), or partially andromonoecious (producing male, female, bisexual, and hermaphrodite flowers) within the same plant. Sex determination of individual floral buds and the distribution of the different flower types on the plant, are both controlled by ethylene. A single missense mutation in the ethylene biosynthesis gene CitACS4, is able to promote the conversion of female into hermaphrodite flowers, and therefore of monoecy (genotype MM) into partial andromonoecy (genotype Mm) or andromonoecy (genotype mm). We phenotyped and genotyped, for the M/m locus, a panel of 207 C. lanatus accessions, including five inbreds and hybrids, and found several accessions that were repeatedly phenotyped as PA (partially andromonoecious) in several locations and different years, despite being MM. A cosegregation analysis between a SNV in CitACS4 and the PA phenotype, demonstrated that the occurrence of bisexual and hermaphrodite flowers in a PA line is not dependent on CitACS4, but conferred by an unlinked recessive gene which we called pa. Two different approaches were performed to map the pa gene in the genome of C. lanatus: bulk segregant analysis sequencing (BSA-seq) and genome wide association analysis studies (GWAS). The BSA-seq study was performed using two contrasting bulks, the monoecious M-bulk and the partially andromonoecious PA-bulk, each one generated by pooling DNA from 20 F2 plants. For GWAS, 122 accessions from USDA gene bank, already re-sequenced by genotyping by sequencing (GBS), were used. The combination of the two approaches indicates that pa maps onto a genomic region expanding across 32.24-36.44 Mb in chromosome 1 of watermelon. Fine mapping narrowed down the pa locus to a 867 Kb genomic region containing 101 genes. A number of candidate genes were selected, not only for their function in ethylene biosynthesis and signalling as well as their role in flower development and sex determination, but also by the impact of the SNPs and indels differentially detected in the two sequenced bulks.