14-3-3 Gene of Zostera Japonica ZjGRF1 Participates in Gibberellin Signaling Pathway

Background Zostera japonica (Z. japonica) is a unique seagrass species in Asia, which has important ecological value. Gibberellin is an important plant hormone, which plays an important role in the regulation of plant growth and development, including seed longevity, seed germination, anti-aging, hypocotyl elongation, leaf development, reproductive organ development and abiotic stress. However, the role of 14-3-3 gene of Z. japonica in GA signaling pathway is still unclear. Methods and results Here, we found that the gibberellin content of Arabidopsis overexpressing ZjGRF1, 14-3-3 gene of Z. japonica, is lower than that of wild type (WT), and the expression of gibberellin synthesis genes is lower than that of WT. The expression level of gibberellin receptors in transgenic ZjGRF1 Arabidopsis was lower than that in WT. The expression level of GA response genes EXP8 in transgenic ZjGRF1 Arabidopsis was lower than that in WT, and the expression levels of PRE1, PRE5 and SCL3 were higher than that in WT. Transgenic ZjGRF1 Arabidopsis is insensitive to paclobutrazol, an inhibitor of gibberellin synthesis. The expression level of flowering regulatory genes in transgenic ZjGRF1 Arabidopsis was lower than that in WT. Conclusion This is the first report on the function of 14-3-3 gene family in seagrass. Our findings can be further utilized in future studies on regulation of 14-3-3 gene on plant development.

Overexpression of GmGAMYB Accelerates the Transition to Flowering and Increases Plant Height in Soybean

The flowering time and plant height of soybean are important agronomic characters, which control the adaptability and yield of soybean. R2R3 MYB transcription factor plays an important regulatory role in plant growth and development. In this study, soybean GmGAMYB gene of R2R3-MYB type was induced by long-days (LDs). GmGAMYB showed higher transcriptional levels in the flowers, leaves and pods of soybean. Overexpression of GmGAMYB in transgenic soybean showed earlier flowering time and maturity in LDs and short-days (SDs). GmGAMYB interacted with GmGBP1 and might promote flowering time by up-regulating the expression of GmFULc gene in soybean. Moreover, the expression level of GmGAMYB was also induced by gibberellins (GAs) and the plant height of GmGAMYB-ox plants was significantly increased, which was caused by the enlargement of internode cell in stem. Furthermore, GmGAMYB overexpression led to increased GA sensitivity in the hypocotyl of soybean seedlings compared with WT. GmGAMYB may be a positive regulator of GA response of promoting plant height by up-regulating the expression of GmGA20ox gene in soybean. Together, our studies preliminarily showed that the partial functions of GmGAMYB in regulating flowering time and GA pathway.

Genome-wide characterization of the WAK gene family and expression analysis under plant hormone treatment in cotton

Background Wall-associated kinases (WAK), one of the receptor-like kinases (RLK), function directly in the connection and communication between the plant cell wall and the cytoplasm. WAK genes are highly conserved and have been identified in plants, such as rice, but there is little research on the WAK gene family in cotton. Results In the present study, we identified 29 GhWAK genes in Gossypium hirsutum. Phylogenetic analysis showed that cotton WAK proteins can be divided into five clades. The results of synteny and Ka/Ks analysis showed that the GhWAK genes mainly originated from whole genome duplication (WGD) and were then mainly under purifying selection. Transcriptome data and real-time PCR showed that 97% of GhWAK genes highly expressed in cotton fibers and ovules. β-glucuronidase (GUS) staining assays showed that GhWAK5 and GhWAK16 expressed in Arabidopsis leaf trichomes. Fourteen GhWAK genes were found to possess putative gibberellin (GA) response elements in the promoter regions, 13 of which were significantly induced by GA treatment. Ten GhWAK genes contained auxin (IAA) response elements and the expression level of nine GhWAKs significantly increased under auxin treatment. Conclusions We provide a preliminary analysis of the WAK gene family in G. hirsutum, which sheds light on the potantial roles of GhWAK genes in cotton fiber cell development. Our data also provides a useful resource for future studies on the functional roles of GhWAK genes.

The Crosstalk between MicroRNAs and Gibberellin Signaling in Plants

Gibberellin (GA) is an integral phytohormone that plays prominent roles in controlling seed germination, stem elongation, leaf development and floral induction. It has been shown that GA regulates these diverse biological processes mainly through overcoming the suppressive effects of the DELLA proteins, a family of nuclear repressors of GA response. MicroRNAs (miRNAs), which have been identified as master regulators of gene expression in eukaryotes, are also involved in a wide range of plant developmental events through the repression of their target genes. The pathways of GA biosynthesis and signaling, as well as the pathways of miRNA biogenesis and regulation, have been profoundly delineated in the past several decades. Growing evidence has shown that miRNAs and GAs are coordinated in regulating plant development, as several components in GA pathways are targeted by miRNAs, and GAs also regulate the expression of miRNAs or their target genes vice versa. Here, we review the recent advances in our understanding of the molecular connections between miRNAs and GA, with an emphasis on the two miRNAs, miR156 and miR159.

The tomato DELLA protein PROCERA promotes ABA responses in guard cells by upregulating ABA transporter

Plants reduce transpiration to avoid drought stress by stomatal closure. While abscisic acid (ABA) has a central role in the regulation of stomatal closure under water-deficit conditions, we demonstrated in tomato that the gibberellin (GA) response inhibitor, the DELLA protein PROCERA (PRO), promotes ABA-induced stomatal closure and gene transcription in guard cells. To study how PRO affects stomatal closure, we performed RNAseq analysis of isolated guard cells and identified the ABA transporters ABA-IMPORTING TRANSPORTER1.1 (AIT1.1) and AIT1.2, also called in Arabidopsis NPF4.6, as upregulated by PRO. Tomato has four AIT1 genes, but only AIT1.1 and AIT1.2 were upregulated by PRO, and only AIT1.1 exhibited high expression in guard cells. Functional analysis of AIT1.1 in yeast confirmed its activity as an ABA transporter, possibly importer. CRISPR-Cas9-defrived ait1.1 mutant exhibited increased transpiration, larger stomatal aperture and reduced response to ABA. Moreover, ait1.1 suppressed the promoting effects of PRO on ABA-induced stomatal closure and gene expression in guard cells. The negative interaction between GA and ABA has been studied for many years in numerous plant species. These studies suggest that the crosstalk is mediated by changes in hormone biosynthesis and signaling. Our results suggest that it is also mediated by changes in hormone transport.One-sentence SummaryThe tomato DELLA protein PROCERA promoted abscisic acid-induced stomatal closure and gene expression by upregulating the expression of the ABA transporter ABA-IMPORTING TRANSPORTER 1 in guard cells.

Gibberellin response in the embryo epidermis regulates germination uniformity in response to seed priming

ABSTRACTUniformity in seed germination remains a primary objective in plant-based food production systems, ensuring predictable and synchronized harvest dates, while suppressing weeds. Treatments including priming can be used to increase germination uniformity and increase the value of commercial seeds. Despite the economic and agronomic importance of seed enhancement treatments, little is known as to how they work at a mechanistic level. Using a combination of molecular genetics and microscopy, we established that hydropriming limits embryo growth genetic programs at an early stage of germination. Conversely, gibberellin (GA) and abscisic acid (ABA)-associated molecular processes progress to later stages of this developmental chronology. The response to GA was specifically affected in the epidermis of germinating embryos in response to hydropriming based on reporter gene expression. The reduction of GA response specifically in the embryo epidermis resulted in increased uniformity of seed germination following hydropriming relative to control seeds. This represents the identification of both a molecular signalling pathway and cell type that are acting to enhance the agronomic germination properties of seed populations. This provides molecular and cellular targets which may be genetically manipulated to enhance seed germination and food production in agronomic species.

Evolution of growth-promoting plant hormones

The plant growth hormones auxin, gibberellins (GAs) and brassinosteroids (BRs) are major determinants of plant growth and development. Recently, key signalling components for these hormones have been identified in vascular plants and, at least for the GAs and BRs, biosynthetic pathways have been clarified. The genome sequencing of a range of species, including a few non-flowering plants, has allowed insight into the evolution of the hormone systems. It appears that the moss Physcomitrella patens can respond to auxin and contains key elements of the auxin signalling pathway, although there is some doubt as to whether it shows a fully developed rapid auxin response. On the other hand, P. patens does not show a GA response, even though it contains genes for components of GA signalling. The GA response system appears to be more advanced in the lycophyte Selaginella moellendorffii than in P. patens. Signalling systems for BRs probably arose after the evolutionary divergence of the mosses and vascular plants, although detailed information is limited. Certainly, the processes affected by the growth hormones (e.g. GAs) can differ in the different plant groups, and there is evidence that with the evolution of the angiosperms, the hormone systems have become more complex at the gene level. The intermediate nature of mosses in terms of overall hormone biology allows us to speculate about the possible relationship between the evolution of plant growth hormones and the evolution of terrestrial vascular plants in general.

Identification, genetic characterization, GA response and molecular mapping of Sdt97: a dominant mutant gene conferring semi-dwarfism in rice (Oryza sativa L.)

SummarySemi-dwarfism is an important agronomic trait in rice breeding programmes. sd-1, termed the ‘Green Revolution gene’, confers semi-dwarf stature, increases harvest index, improves lodging resistance, and is associated with increased responsiveness to nitrogen fertilizer. It has contributed substantially to the significant increase in rice production. In this paper, a novel semi-dwarf mutant in rice is reported. Genetic analysis revealed that only a single dominant gene locus non-allelic to sd-1, temporarily designated Sdt97, is involved in the control of semi-dwarfism of the mutant. The semi-dwarfism of the mutant could be partly restored to the tall wild-type by application of exogenous GA3, suggesting that the mutant gene Sdt97 may be involved in the gibberellin (GA) synthesis pathway and not the GA response pathway in rice. A residual heterozygous line (RHL) population derived from a recombinant inbred line (RIL) was developed. Simple sequence repeat (SSR) and bulked segregation analysis (BSA) combined with recessive class analysis (RCA) techniques were used to map Sdt97 to the long arm of chromosome 6 at the interval between two STS markers, N6 and TX5, with a genetic distance of 0·2 cM and 0·8 cM, respectively. A contig map was constructed based on the reference sequence aligned by the Sdt97 linked markers. The physical map of the Sdt97 locus was defined to a 118 kb interval, and 19 candidate genes were detected in the target region. This is the first time that a dominant semi-dwarf gene has been reported in rice. Cloning and functional analysis of gene Sdt97 will help us to learn more about molecular mechanism of rice semi-dwarfism.