GIBBERELLIN INSENSITIVE DWARF1 Research Articles

Effect of a novel dwarfing mutant site on chromosome 4B on agronomic traits in common wheat.

The introduction of dwarfing genes triggered a wave of "green revolution". A number of wheats dwarfing genes have been reported in previous studies, and only a small fraction of these have been applied to production practices. Therefore, the development of novel dwarfing genes for wheat is of great value. In this study, a novel dwarfing site, Rht-yz, identified in the Yanzhan mutation, is located on chromosome 4B (30-33MB) and its mechanism of action is different from that of Rht-B1b (C-T mutation), but whether it affects the Rht-B1a (TraesCS4B02G043100) or other genes is unclear. Exogenously applied GA3 experiments showed that Rht-yz is one of the gibberellin-insensitive dwarf genes. The effects of the dwarf gene Rht-yz on agronomic traits in wheat were evaluated in the field using Yanzhan, Yanzhan mutations, F2:3 and F3:4 lines. The results showed that Rht-yz improved lodging resistance by reducing plant height, increasing diameter, wall thickness and mechanical strength of the basal stem. In terms of yield traits, Rht-yz had negative effects on tiller number plant-1, biomass plant-1 and yield plant-1, but had no significant effect on harvest index, 1000-kernel weight and spike traits. In addition, Rht-yz significantly increased crude protein, wet gluten and starch content. Therefore, the rational use of the new dwarfing site Rht-yz has potential and value in dwarf wheat breeding.

The F-box protein RhSAF destabilizes the gibberellic acid receptor RhGID1 to mediate ethylene-induced petal senescence in rose.

Roses are among the most popular ornamental plants cultivated worldwide for their great economic, symbolic, and cultural importance. Nevertheless, rapid petal senescence markedly reduces rose (Rosa hybrida) flower quality and value. Petal senescence is a developmental process tightly regulated by various phytohormones. Ethylene accelerates petal senescence, while gibberellic acid (GA) delays this process. However, the molecular mechanisms underlying the crosstalk between these phytohormones in the regulation of petal senescence remain largely unclear. Here, we identified SENESCENCE-ASSOCIATED F-BOX (RhSAF), an ethylene-induced F-box protein gene encoding a recognition subunit of the SCF-type E3 ligase. We demonstrated that RhSAF promotes degradation of the GA receptor GIBBERELLIN INSENSITIVE DWARF1 (RhGID1) to accelerate petal senescence. Silencing RhSAF expression delays petal senescence, while suppressing RhGID1 expression accelerates petal senescence. RhSAF physically interacts with RhGID1s and targets them for ubiquitin/26S proteasome-mediated degradation. Accordingly, ethylene-induced RhGID1C degradation and RhDELLA3 accumulation are compromised in RhSAF-RNAi lines. Our results demonstrate that ethylene antagonizes GA activity through RhGID1 degradation mediated by the E3 ligase RhSAF. These findings enhance our understanding of the phytohormone crosstalk regulating petal senescence and provide insights for improving flower longevity.

Cucumber mosaic virus-induced gene and microRNA silencing in water dropwort (Oenanthe javanica (Blume) DC)

Water dropwort (Oenanthe javanica (Blume) DC), an aquatic perennial plant from the Apiaceae family, rich in dietary fibert, vitamins, and minerals. It usually grows in wet soils and water. Despite accumulating the transcriptomic data, gene function research on water dropwort is still far behind than that of the other crops. The cucumber mosaic virus (CMV) induced gene silencing was established to study the functions of gene and microRNA (miRNA) in the water dropwort. CMV Fast New York strain (CMV-Fny) genomic RNAs 1, 2, and 3 were individually cloned into pCB301 vectors. We deleted part of the ORF 2b region and introduced recognition sites. A CMV-induced gene silencing vector was employed to suppress the expression of endogenous genes, including phytoene desaturase (PDS). In order to assess the efficacy of gene silencing, we also cloned conserved sequence of gibberellin insensitive dwarf (GID1) cDNA sequences into the vector and inoculated the water dropwort. The height of CMV-GID1-infected plants was marginally reduced as a result of GID1 gene silencing, and their leaves were noticeably longer and thinner. Additionally, we also used a CMV-induced silencing vector to analyze the roles of endogenous miRNAs. We used a short tandem target mimic approach to clone miR319 and miR396 from water dropwort into the CMV vector. Plants with CMV-miRNA infection were driven to exhibit the distinctive phenotypes. We anticipate that functional genomic research on water dropwort will be facilitated by the CMV-induced gene silencing technique.

The interactions of Rht15 and Rht1 alleviate some of their negative effects on agronomic traits in durum wheat

The application of dwarfing genes in wheat breeding effectively reduced plant height, improved lodging resistance and increased the harvest index. Although the gibberellin-responsive (GAR) dwarf gene Rht15 did not negatively affect coleoptile length or root traits while reducing the plant height, it reduced the yield plant−1. The gibberellin-insensitive (GAI) dwarf gene Rht1 can increase wheat yield under favorable conditions, but it reduces coleoptile length and affects root traits. This study was conducted to investigate whether the interaction of Rht15 and Rht1 can alleviate their negative effects. To analyze the interaction of Rht15 and Rht1, field experiments were conducted with the F5, F6 and F7 lines of the four genotypes, Rht15+Rht1, Rht15, Rht1 and tall lines detected using Rht15 and Rht1 molecular markers, derived from Durox (Rht15) and Kronos (Rht1), by comparing their effects on seedling traits, plant height and internode length, lodging resistance, flag leaf, yield and quality traits in durum wheat. The results showed that although the interaction of Rht15 and Rht1 did not overcome the inhibitory effect of Rht1 on coleoptile growth, it alleviated the negative effect of Rht1 on maximum root length (+14.8%). The grain yield plant−1 (+7.2%) of the Rht15 lines was improved under the action of Rht1 but was still lower than that of the Rht1 lines (−12.7%). The Rht15+Rht1 lines had the strongest effect on reducing plant height and center of gravity height (−42.2% and −41.5%), which significantly improved lodging resistance (+175%). The flag leaf area (+97.4%) and SPAD value (+11.6%, +9.6% and +10.6%) were also significantly increased. In addition, the coleoptile length of the Rht15 lines was not significantly different from that of the tall lines, the plant height and center of gravity height were significantly reduced (−30.5% and −34.0%), and the lodging resistance was significantly increased (+176.8%). The Rht1 lines had increased grain yield (+12.7%) due to an increased 1000-kernel weight (+12.9%) compared to the tall lines. In conclusion, the combination of Rht15 and Rht1 alleles enhanced the advantages and partially alleviated the defects in some traits when compared to the individual alleles, but the grain yield plant−1 was still lower than the Rht1 lines. This reflected the limitations of Rht15, and further confirmed the yield advantages of Rht1.

Transcriptome Analysis Reveals the Role of Phytohormones in the Distant Hybridization of Peony Embryo Abortion

Peonies are significant ornamental plants that are primarily propagated through distant cross-breeding to create new varieties. However, hybrid failure is a critical issue that impedes the advancement of breeding. Numerous studies have demonstrated that endogenous hormones in the seed embryo constitute a significant factor in embryo failure. Nevertheless, it is still unknown how plant hormones control the development of peony embryos at the molecular level. In this study, we characterized the endogenous hormone levels in peony seeds of hybrid-aborted, hybrid-normal, and self-crossing normal after 26 days of pollination (DAP). Our findings show that the hybrid-aborted embryos had significantly higher amounts of ABA, IAA, and GA. In addition, the ratio of GA+IAA/ABA was lower than that of the hybrid-normal seeds and higher than that of the self-crossing normal seeds. To further investigate the mechanism of hormone control on peony embryo development, we conducted a transcriptome sequencing analysis of the three seed types. Results revealed that differentially expressed genes involved in phytohormone metabolism and signal transduction significantly enriched the aborted embryos. Furthermore, we examined the expression levels of six hormones in different seeds and used the Gene Common Expression Trend analysis to analyze genes highly correlated with phytohormone in the KEGG pathway. We used protein interaction networks to explore the interactions between proteins in the hormone pathway in aborted embryos. Then we identified key genes and transcription factors (TFs) such as Abscisic acid-insensitive 5 (ABI5), Auxin Response Factor 5 (ARF5), Gibberellin Insensitive Dwarf 1 (GID1), Arabidopsis Response Regulator4 (ARR4), Jasmonate-zim-domain protein 1 (JAZ1), Brassinazole-resistant 1 (BZR1), etc., whose functions require further investigation. Our findings establish a foundation for the metabolic regulation of peony hybrid embryo abortion via networks regulating phytohormone signaling. However, further research is needed to determine the exact mechanisms by which hormones regulate peony embryo development and to explore new methods for improving the success rate of hybridization.

A non-canonical function of Arabidopsis ERECTA proteins and a role of the SWI3B subunit of the SWI/SNF chromatin remodeling complex in gibberellin signaling.

The Arabidopsis ERECTA family (ERf) of leucine-rich repeat receptor-like kinases (LRR-RLKs) comprising ERECTA (ER), ERECTA-LIKE 1 (ERL1), and ERECTA-LIKE 2 (ERL2) controls epidermal patterning, inflorescence architecture, and stomata development and patterning. These proteins are reported to be plasma membrane associated. Here we show that the er/erl1/erl2 mutant exhibits impaired gibberellin (GA) biosynthesis and perception alongside broad transcriptional changes. The ERf kinase domains were found to localize to the nucleus where they interact with the SWI3B subunit of the SWI/SNF chromatin remodeling complex (CRCs). The er/erl1/erl2 mutant exhibits reduced SWI3B protein level and affected nucleosomal chromatin structure. Similar to swi3c and brm plants with inactivated subunits of SWI/SNF CRCs, it also does not accumulate DELLA RGA and GAI proteins. The ER kinase phosphorylates SWI3B in vitro, and the inactivation of all ERf proteins leads to the decreased phosphorylation of SWI3B protein in vivo. The identified correlation between DELLA overaccumulation and SWI3B proteasomal degradation, and the physical interaction of SWI3B with DELLA proteins indicate an important role of SWI3B-containing SWI/SNF CRCs in gibberellin signaling. Co-localization of ER and SWI3B on GID1 (GIBBERELLIN INSENSITIVE DWARF 1) DELLA target gene promoter regions and abolished SWI3B binding to GID1 promoters in er/erl1/erl2 plants supports the conclusion that ERf-SWI/SNF CRC interaction is important for transcriptional control of GA receptors. Thus, the involvement of ERf proteins in the transcriptional control of gene expression, and observed similar features for human HER2 (epidermal growth family receptor member), indicate an exciting target for further studies of evolutionarily conserved non-canonical functions of eukaryotic membrane receptors.

Structural Elucidation of Relevant Gibberellic Acid Impurities and In Silico Investigation of Their Interaction with Soluble Gibberellin Receptor GID1.

Gibberellin derivatives are a family of tetracyclic diterpenoid plant hormones used in agriculture as plant growth regulators included in the European Directive 91/414. In the pesticide peer review process and to assess their toxicological relevance and product chemical equivalence, the European Food Safety Authority (EFSA) highlighted data gaps such as the identification of hydrolysis products and unknown impurities. The aspect of impurity characterization and quantitation is challenging and requires the use of hyphenated analytical techniques. In this regard, we used an LC-QTOF/MS and NMR analysis for the characterization of gibberellic acid impurities found in technical products. Gibberellic acid impurities such as gibberellin A1 (GA 1 ), 3-isolactone gibberellic acid (iso-GA 3 ), gibberellenic acid, 1α,2α-epoxygibberellin A3 (2-epoxy- GA 3 ), and (1α,2β,3α,4bβ,10β)-2,3,7-trihydroxy-1-methyl-8-methylenegibb-4-ene-1,10-dicarboxylic acid were identified and successfully characterized. Moreover, an in silico investigation on selected gibberellic acid impurities and derivatives and their interactions with a gibberellin insensitive dwarf1 (GID1) receptor has been carried out by means of induced fit docking (IFD), generalized-Born surface area (MM-GBSA), and metadynamics (MTD) experiments. A direct HPLC method with DAD and MS for the detection of gibberellic acid and its impurities in a technical sample has been developed. Moreover, by means of the in silico characterization of the GID1 receptor-binding pocket, we investigated the receptor affinity of the selected gibberellins, identifying compounds (2) and (4) as the most promising hit to lead compounds.

Cloning and Functional Identification of Gibberellin Receptor SvGID1s Gene of Salix viminalis.

Gibberellins (GAs) play a key role in the transition from vegetative growth to flowering and the GA receptor GID1 (GIBBERELLIN INSENSITIVE DWARF1) is the central part of GA-signaling. The differential expression of SvGID1 was found in the transcriptome sequencing in our previous study, which was further verified at different stages of flowering of Salix viminalis. In order to reveal the function GID1 of S. viminalis, two genes of SvGID1b and SvGID1c were cloned and transformed into Arabidopsis thaliana, respectively. The results showed that the full ORF length of SvGID1b and SvGID1c genes were both 1035bp, encoding 344 amino acids, which were typical globular proteins. The peptide chain contained more α-helix structure, and had 99% similarity with GID1b and GID1c amino acid sequences of Salix suchowensis. Phylogenetic analysis showed that SvGID1s had close genetic relationship with woody plants such as Populus alba and Populus tomentosa, and had far genetic relationship with rice. After overexpression in A. thaliana, the total gibberellin, active gibberellin content and the expression level of GA3ox1, the key gene for GA4 synthesis, were not significantly different from those in the wild-type, while the expression levels of FUL, SOC1 and FT, the key genes for flowering in plants, were increased, and the expression levels of FLC and GAI were decreased. The ectopic expression of SvGID1s increased the sensitivity of plants to gibberellin and enhanced gibberellin effect, caused early bolting, budding and flowering, led to higher plant, longer hypocotyl and other phenomena. The results provide a theoretical basis for clarifying the regulation of gibberellin on flower bud differentiation of flowering plants.

Evaluating the impact of Rht hypomorphic mutations in durum wheat

AbstractIncreasing the yield of wheat (Triticum spp.) requires identifying new allelic combinations by crossing or by creating useful variation in yield limiting genes. Wheat yield is impacted by many factors, including tiller number and seeds per tiller, both of which are impacted by the Reduced height (Rht) gene. Durum wheat [T. turgidum L. subsp. durum (Desf.) van Slageren] varieties are either standard height, wild type for Rht (Rht‐B1a), or are semidwarf and carry the Rht‐B1b allele. Rht‐B1b increases productive tillers but can result in plants too short for easy harvest in the northern United States and shorter coleoptiles that reduce dry soil germination. In this study, durum plants varying for Rht alleles created by ethyl methanesulfonate (EMS) mutagenesis were studied to determine the impact of each allele upon agronomic and seed traits. The projects’ goal is to increase durum wheat yield through the development of a plant with height intermediate between current full‐height and semidwarf varieties. Experiments included field trials, coleoptile length and gibberellic acid (GA) responsiveness assays, and an in vitro test to determine the impact of each Rht mutation upon binding to Gibberellin Insensitive Dwarf1 (GID1). It was found that the Rht‐B1b‐E529K allele conferred plant height and coleoptile length intermediate between Rht‐B1b and Rht‐B1a containing plants, while two Rht‐A1 alleles had lesser impacts with trends toward intermediate‐height plants. The results of this research demonstrate that hypomorphic Rht alleles that alter Rht binding to GID1 may prove useful in optimizing durum wheat height to increase yield across different growing conditions.

Endodormancy Release Can Be Modulated by the GA4-GID1c-DELLA2 Module in Peach Leaf Buds.

Gibberellin (GA) plays a key role in the release of bud dormancy and the GA receptor GID1 (GIBBERELLIN INSENSITIVE DWARF1) and DELLA protein are the GA signaling parts, but the molecular mechanism of GA-GID1-DELLA module regulating leaf bud dormancy in peach (Prunus persica) is still not very clear. In this study, we isolated and characterized the GID1 gene PpGID1c from the peach cultivar “Zhong you No.4.” Overexpressing PpGID1c in Arabidopsis promoted seed germination, which indicated that PpGID1c has an important function in dormancy. The expression level of PpGID1c in peach leaf buds during endodormancy release was higher than that during ecodormancy and was positively correlated with GA4 levels. Our study also found that GA4 had the most obvious effect on promoting the bud break, indicating that GA4 may be the key gibberellin to promoting peach leaf bud endodormancy release. Moreover, a quantitative real-time PCR (qRT-PCR) found that GA4 could increase the expression of the gibberellin signaling gene PpDELLA2. A yeast two-hybrid (Y2H) assay suggested that the PpGID1c interaction with the PpDELLA1 protein was not dependent on gibberellin, while the PpGID1c interaction with PpDELLA2 required GA4 or another gibberellin. These findings suggested that the GA4-GID1c-DELLA2 module regulates peach leaf bud endodormancy release, with this finding significantly enhancing our comprehensive understanding of bud endodormancy release and revealing a new mechanism for regulating leaf bud endodormancy release in peach.

Physiological and gene expression changes during imbibition in maize seeds under low temperature conditions

Maize is one of the most important crop species worldwide, but also extremely susceptible to the effects of increasingly higher temperatures and drought during the summer and its flowering and grain filling stage. Different strategies are being utilized to ensure a satisfying yield potential and quality even in the extremely unfavourable environmental conditions, which are the result of climate change. Some of them are cropping pattern changes and sowing alterations, including earlier sowing. Since this implies the exposure to suboptimal temperatures during early developmental stages, it leads to a demand for developing maize lines tolerant to low temperatures during these stages. This research focuses on the first phase of germination, imbibition. Maize tolerance to low temperatures is a complex trait that includes different mechanisms and strategies that all work together to ensure adaptation and survival, such as cell membrane changes, antioxidative system activation, etc. Additionally, the low temperature response of different maize inbreds varies substantially, so recognizing the different ways in which they respond to low temperatures during imbibition and other earlier stages of development is crucial. To accomplish this, seeds of two maize inbred lines of contrasting susceptibility to low temperatures were selected and exposed to control (20? C) and low temperature (8?C) conditions during the first 24h of imbition and then further analyzed to assess their response. This included germination and tetrazolium assays; ascertaining membrane integrity by evaluating cell leakage and lipid peroxidation; determining the antioxidative capacity by assessing superoxide dismutase (SOD) and catalase (CAT) activity; and expression analysis of four genes included in the low temperature response (gibberellin insensitive dwarf 1 gibberellin receptor, gid1; fatty acid desaturases 2 and 6, fad2 and fad6; plastid-lipid-associated 2 protein, pap2). The results showed that, while there is not a significant difference in their germination rate, they differ in their survival rate, with more seeds of the tolerant genotype surviving the low temperature period. Significant differences between them were found in cell leakage (p<0,01), as well as gid1(p<0,05) and fad6 (p<0,05) gene expression assays. The present research brings light to our understanding of the effect of low temperatures on the first germination stage, - imbibition. It highlights the importance of choosing the right inbreds for earlier sowing and points to certain routes that could be taken for improving and accelerating the breeding process for low temperature tolerance.

The Allelic Diversity of the Gibberellin Signaling Pathway Genes in Aegilops tauschii Coss.

Gibberellin-insensitive reduced height genes are widely spread in modern wheat varieties, making them resistant to lodging under conditions of intensive farming. However, the limited diversity of these genes present in wheat germplasm can limit the adaptability of newly created cultivars to the changing climate. The diversity of the gibberellin signaling pathway genes involved in plant height control—Reduced height 1 (Rht-D1), Gibberellin-insensitive dwarf 1 (Gid1-D) and Gibberellin-insensitive dwarf 2 (Gid2-D)—was studied in the diploid wild goatgrass Aegilops tauschii Coss., one of the ancestral species of the bread wheat (Triticum aestivum L.) and the donor of its D subgenome, using high-throughput sequencing. The examination of 24 Ae. tauschii accessions of different geographical origins revealed a large number of new alleles (haplotypes) not found in bread wheat varieties. Some of the detected polymorphisms lead to changes in the amino acid sequence of proteins. Four isoforms (amino acid sequence variants) were found for the RHT-D1 protein, and two isoforms—for the GID1 and GID2 proteins, each. An analysis of the co-occurrence frequencies of various isoforms of the three proteins showed that their combinations were not random in Ae. tauschii, which may indicate the functional significance of their differences. New alleles of the Rht-D1, Gid1-D, and Gid2-D genes are promising for introgression into bread wheat and studying their effect on plant height and adaptability.

Wheat growth responses to soil mechanical impedance are dependent on phosphorus supply

Increased mechanical impedance induced by soil drying or compaction causes reduction in plant growth and crop yield. However, how mechanical impedance interacts with nutrient stress has been largely unknown. Here, we investigated the effect of mechanical impedance on the growth of wheat seedlings under contrasting phosphorus (P) supply in a sand culture system which allows the mechanical impedance to be independent of water and nutrient availability. Two wheat genotypes containing the Rht-B1a (tall) or Rht-B1c (gibberellin-insensitive dwarf) alleles in the Cadenza background were used and their shoot and root traits were determined. Mechanical impedance caused a significant reduction in plant growth under sufficient P supply, including reduced shoot and root biomass, leaf area and total root length. By contrast, under low P supply, mechanical impedance did not affect biomass, tiller number, leaf length, and nodal root number in both wheat genotypes, indicating that the magnitude of the growth restriction imposed by mechanical impedance was dependent on P supply. The interaction effect between mechanical impedance and P level was significant on most plant traits except for axial and lateral root length, suggesting an evident physical and nutritional interaction. Our findings provide valuable insights into the integrated effects of plants in response to both soil physical and nutritional stresses. Understanding the response patterns is critical for optimizing soil tillage and nutrient management in the field.

Mutations in the tomato gibberellin receptors suppress xylem proliferation and reduce water loss under water-deficit conditions.

Low gibberellin (GA) activity in tomato (Solanum lycopersicum) inhibits leaf expansion and reduces stomatal conductance. This leads to lower transpiration and improved water status under transient drought conditions. Tomato has three GIBBERELLIN-INSENSITIVE DWARF1 (GID1) GA receptors with overlapping activities and high redundancy. We tested whether mutation in a single GID1 reduces transpiration without affecting growth and productivity. CRISPR-Cas9 gid1 mutants were able to maintain higher leaf water content under water-deficit conditions. Moreover, while gid1a exhibited normal growth, it showed reduced whole-plant transpiration and better recovery from dehydration. Mutation in GID1a inhibited xylem vessel proliferation, which led to lower hydraulic conductance. In stronger GA mutants, we also found reduced xylem vessel expansion. These results suggest that low GA activity affects transpiration by multiple mechanisms: it reduces leaf area, promotes stomatal closure, and reduces xylem proliferation and expansion, and as a result, xylem hydraulic conductance. We further examined if gid1a performs better than the control M82 in the field. Under these conditions, the high redundancy of GID1s was lost and gid1a plants were semi-dwarf, but their productivity was not affected. Although gid1a did not perform better under drought conditions in the field, it exhibited a higher harvest index.

Gibberellin Signaling Repressor LlDELLA1 Controls the Flower and Pod Development of Yellow Lupine (Lupinus luteus L.).

Precise control of generative organ development is of great importance for the productivity of crop plants, including legumes. Gibberellins (GAs) play a key role in the regulation of flowering, and fruit setting and development. The major repressors of GA signaling are DELLA proteins. In this paper, the full-length cDNA of LlDELLA1 gene in yellow lupine (Lupinus luteus L.) was identified. Nuclear-located LlDELLA1 was clustered in a second phylogenetic group. Further analyses revealed the presence of all conserved motifs and domains required for the GA-dependent interaction with Gibberellin Insensitive Dwarf1 (GID1) receptor, and involved in the repression function of LlDELLA1. Studies on expression profiles have shown that fluctuating LlDELLA1 transcript level favors proper flower and pod development. Accumulation of LlDELLA1 mRNA slightly decreases from the flower bud stage to anther opening (dehiscence), while there is rapid increase during pollination, fertilization, as well as pod setting and early development. LlDELLA1 expression is downregulated during late pod development. The linkage of LlDELLA1 activity with cellular and tissue localization of gibberellic acid (GA3) offers a broader insight into the functioning of the GA pathway, dependent on the organ and developmental stage. Our analyses provide information that may be valuable in improving the agronomic properties of yellow lupine.

A New Insight into Flowering Regulation: Molecular Basis of Flowering Initiation in Magnolia × soulangeana 'Changchun'.

Magnolia × soulangeana ‘Changchun’ are trees that bloom in spring and summer respectively after flower bud differentiation. Here, we use phenological and morphological observation and RNA-seq technology to study the molecular basis of flowering initiation in ‘Changchun’. During the process of flowering initiation in spring and summer, the growth of expanded flower buds increased significantly, and their shape was obviously enlarged, which indicated that flowering was initiated. A total of 168,120 expressed genes were identified in spring and summer dormant and expanded flower buds, of which 11,687 genes showed significantly differential expression between spring and summer dormant and expanded flower buds. These differentially expressed genes (DEGs) were mainly involved in plant hormone signal transduction, metabolic processes, cellular components, binding, and catalytic activity. Analysis of differential gene expression patterns revealed that gibberellin signaling, and some transcription factors were closely involved in the regulation of spring and summer flowering initiation in ‘Changchun’. A qRT-PCR (quantitative Real Time Polymerase Chain Reaction) analysis showed that BGISEQ-500 sequencing platform could truly reflect gene expression patterns. It also verified that GID1B (GIBBERELLIN INSENSITIVE DWARF1 B), GID1C, SPL8 (SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 8), and GASA (GIBBERELLIC ACID-STIMULATED ARABIDOPSIS) family genes were expressed at high levels, while the expression of SPY (SPINDLY) was low during spring and summer flowering initiation. Meanwhile, the up- and down-regulated expression of, respectively, AGL6 (AGAMOUS-LIKE 6) and DREB3 (DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN 3), AG15, and CDF1 (CYCLIC DOF FACTOR 1) might also be involved in the specific regulation of spring and summer flowering initiation. Obviously, flowering initiation is an important stage of the flowering process in woody plants, involving the specific regulation of relevant genes and transcription factors. This study provides a new perspective for the regulation of the flowering process in perennial woody plants.

Computational-Aided Discovery of Novel 1,3-Benzodioxole Plant Growth Retardants

Plant growth retardants can enhance the lodging resistance of crops and prevent yield losses. In this study, we used the crystal structure of the gibberellin receptor GIBBERELLIN INSENSITIVE DWARF1 (GID1) to aid the discovery of novel growth retardants. The Maybridge database was filtered based on multiple-screening analysis, including pharmacophore modeling, target structures, Lipinski’s rules of 5, and physicochemical properties. Finally, the 1,3-benzodioxole compounds were screened and their potential interaction mechanisms, synthesis, and biological activity on the root lengths of wild-type and mutant-type Arabidopsis thaliana were investigated. The results showed that the compounds inhibited root growth in WT A. thaliana at a range of concentrations, with optimal inhibition observed at 100 μmol/L. The inhibition by compound HTS05309 was comparable to that of uniconazole (100%). Quantitative experiments confirmed that the compounds inhibited A. thaliana growth. These results suggested that novel plant growth retardants have been identified based on computational-aided discovery.

Multiple Gibberellin Receptors Contribute to Phenotypic Stability under Changing Environments.

The pleiotropic and complex gibberellin (GA) response relies on targeted proteolysis of DELLA proteins mediated by a GA-activated GIBBERELLIN-INSENSITIVE DWARF1 (GID1) receptor. The tomato (Solanum lycopersicum) genome encodes for a single DELLA protein, PROCERA (PRO), and three receptors, SlGID1a (GID1a), GID1b1, and GID1b2, that may guide specific GA responses. In this work, clustered regularly interspaced short palindromic repeats (CRISPR) /CRISPR associated protein 9-derived gid1 mutants were generated and their effect on GA responses was studied. The gid1 triple mutant was extremely dwarf and fully insensitive to GA. Under optimal growth conditions, the three receptors function redundantly and the single gid1 mutants exhibited very mild phenotypic changes. Among the three receptors, GID1a had the strongest effects on germination and growth. Yeast two-hybrid assays suggested that GID1a has the highest affinity to PRO. Analysis of lines with a single active receptor demonstrated a unique role for GID1a in protracted response to GA that was saturated only at high doses. When the gid1 mutants were grown in the field under ambient changing environments, they showed phenotypic instability, the high redundancy was lost, and gid1a exhibited dwarfism that was strongly exacerbated by the loss of another GID1b receptor gene. These results suggest that multiple GA receptors contribute to phenotypic stability under environmental extremes.

GIBBERELLIN INSENSITIVE DWARF1 Plays an Important Role in the Growth Regulation of Dwarf Apple Rootstocks

Dwarfing rootstocks can improve the plant architecture of apple trees and increase production. Gibberellins (GAs) are crucial for plant growth and dwarfing traits. The receptor, GIBBERELLIN INSENSITIVE DWARF1 (GID1), plays an important role in the regulation pathway. However, the growth regulatory mechanism of GID1 in dwarf apple rootstock seedlings is not clear. In this study, we selected dwarf apple rootstock ‘SH6’ and its cross parents as materials to clone the GA receptor gene GID1c. There were two different sites in the alpha/beta hydrolase domain. The expression of GID1c in ‘SH6’ was lower than that in Malus domestica cv. Ralls Janet, with the decrease of GA content. We further conducted GA3 treatment and overexpression of GID1c in tissue culture seedlings of ‘SH6’, and the results showed that the expression of GID1c and biosynthesis genes increased and promoted the accumulation of hormone contents, which ultimately regulates the growth of ‘SH6’ dwarf apple rootstock seedlings. Our results suggest that GID1c may affect the plant architecture and dwarf traits of dwarfing rootstock and accelerate its application in orchards.

Expansion and diversification of the gibberellin receptor GIBBERELLIN INSENSITIVE DWARF1 (GID1) family in land plants

Here we uncover the major evolutionary events shaping the evolution of the GID1 family of gibberellin receptors in land plants at the sequence, structure and gene expression levels. Gibberellic acid (gibberellin, GA) controls key developmental processes in the life cycle of land plants. By interacting with the GIBBERELLIN INSENSITIVE DWARF1 (GID1) receptor, GA regulates the expression of a wide range of genes through different pathways. Here we report the systematic identification and classification of GID1s in 54 plants genomes, encompassing from bryophytes and lycophytes, to several monocots and eudicots. We investigated the evolutionary relationship of GID1s using a comparative genomics framework and found strong support for a previously proposed phylogenetic classification of this family in land plants. We identified lineage-specific expansions of particular subfamilies (i.e. GID1ac and GID1b) in different eudicot lineages (e.g. GID1b in legumes). Further, we found both, shared and divergent structural features between GID1ac and GID1b subgroups in eudicots that provide mechanistic insights on their functions. Gene expression data from several species show that at least one GID1 gene is expressed in every sampled tissue, with a strong bias of GID1b expression towards underground tissues and dry legume seeds (which typically have low GA levels). Taken together, our results indicate that GID1ac retained canonical GA signaling roles, whereas GID1b specialized in conditions of low GA concentrations. We propose that this functional specialization occurred initially at the gene expression level and was later fine-tuned by mutations that conferred greater GA affinity to GID1b, including a Phe residue in the GA-binding pocket. Finally, we discuss the importance of our findings to understand the diversification of GA perception mechanisms in land plants.