Exogenous GA3 Research Articles

The SLR1-OsMADS23-D14 module mediates the crosstalk between strigolactone and gibberellin signaling to control rice tillering.

Strigolactones (SLs) and gibberellins (GAs) have been found to inhibit plant branching or tillering, but molecular mechanisms underlying the interplay between SL and GA signaling to modulate tillering remain elusive. We found that the transcription factor OsMADS23 plays a crucial role in the crosslink between SL and GA signaling in rice tillering. Loss-of-function mutant osmads23 shows normal axillary bud formation but defective bud outgrowth, thus reducing the tiller number in rice, whereas overexpression of OsMADS23 significantly increases tillering by promoting tiller bud outgrowth. OsMADS23 physically interacts with DELLA protein SLENDER RICE1 (SLR1), and the interaction reciprocally stabilizes each other. Genetic evidence showed that SLR1 is required for OsMADS23 to control rice tillering. OsMADS23 acts as an upstream transcriptional repressor to inhibit the expression of SL receptor gene DWARF14 (D14), and addition of SLR1 further enhances OsMADS23-mediated transcriptional repression of D14, indicating that D14 is the downstream target gene of OsMADS23-SLR1 complex. Moreover, application of exogenous SL and GA reduces the protein stability of OsMADS23-SLR1 complex and promotes D14 expression. Our results revealed that SLs and GAs synergistically inhibit rice tillering by destabilizing OsMADS23-SLR1 complex, which provides important insights into the molecular networks of SL-GA synergistic interaction during rice tillering.

Effect of GA3 Spraying on the Physiological and Biochemical Indexes of Aglaonema under Drought Treatment

GA3 is a common plant growth regulator used in production that can accelerate plant metabolism and significantly enhance the plant growth rate. We investigated the effects of exogenous GA3 on the physiological and biochemical indexes of Aglaonema under drought treatment. The effects of exogenous GA3 on the plant height, leaf blight rate, antioxidant enzyme activity, leaf pigment, and malondialdehyde content of Aglaonema were evaluated using Aglaonema ‘Red Ruyi’ as the test material and simulating natural drought treatment in nutrient soil pots. The spraying of exogenous GA3 significantly increased superoxide dismutase and peroxidase enzyme activities, promoted the accumulation of soluble sugars, reduced the accumulation of malondialdehyde, and slowed the decline of chlorophyll and carotenoids, which had good effects such as the reduction of the leaf wilting rate and increase in the plant height as well as the maintenance of the plant shape to maintain the ornamental appearance. The growth indexes such as plant height and wilting rate were mainly influenced by the changes of the leaf pigment and physiological and biochemical indexes of malondialdehyde.

Characterization of SUPPRESSOR OF MAX2 1-LIKE (SMXL) Genes in ‘duli’ (Pyrus betulifolia L.) and Expression Analysis of PbSMXLs in Response to Plant Growth Regulators and Salt Stress

SUPPRESSOR OF MAX2 1-LIKE (SMXL) proteins are negative regulators of strigolactone (SL) signal transduction that play an important role in regulating plant branching and responses to abiotic stress. Here, we studied the role of SMXL proteins in pear growth, development, and stress resistance. A total of 18 SMXL members were characterized in ‘duli’. All SMXL members were localized to chloroplasts. Chromosome mapping analysis showed that the members of this family were unevenly distributed on 14 chromosomes. Gene fragment replication analysis showed that there were no tandem repeat genes in PbSMXLs, and 12 pairs of homologous genes were fragment duplications. There were 30 pairs of homologous genes between ‘duli’ and apples, and 17 between ‘duli’ and Arabidopsis thaliana. Analysis of cis-acting elements showed that there was a large number of photo-effector elements, short-effector elements, hormone-responsive elements, and abiotic stress-responsive elements in the promoter sequences of this family. Analysis of enzyme activity and endogenous SL showed that β-carotenoid isomerase (D27), carotenoid cleavage dioxygenase 7 (CCD7), lateral branch oxidoreductase (LBO) levels, and SL content were higher in ‘duli’ roots and leaves compared in the control under exogenous GA3 (gibberellin 3), IAA (indole-3-acetic acid), GR24 (synthetic SL analog), and NaCl. Most SMXL genes in ‘duli’ were highly expressed in branches and axillary lobes, but their expression was low in fruits. qRT-PCR analysis revealed that eight PbSMXL genes were responsive to GA3, PAC (Paclobutrazol), IAA, ABA (abscisic acid), GR24, and Tis108 (SL biosynthesis inhibitor). PbSMXLs responded positively to salt stress. The expression of PbSMXL6 and PbSMXL15 was significantly induced under salt stress. The expression of PbSMXL7, PbSMXL10, and PbSMXL15 was significantly induced by Tis108 treatment. The results of this study enhance our understanding of the role of SMXL genes in the responses to plant growth regulators and salt stress. Our findings will also aid future studies of the functions of SMXL genes in ‘duli’.

Gibberellin promotes theanine synthesis by relieving the inhibition of CsWRKY71 on CsTSI in tea plant (Camellia sinensis)

Abstract Theanine is a crucial indicator of tea quality, its significance is closely tied to the economic value of tea. There were many reports on the regulation mechanism of theanine synthesis and accumulation, but the mechanism of gibberellin regulates theanine synthesis in tea plants is poorly understood. Previous studies have shown that the content of theanine experiences significant changed in the growth stages of tea shoots, displayed a strong correlation with gibberellin. This study confirmed that gibberellin significantly promoted the expression of the major gene of theanine synthesis, known as CsTSI. Additionally, the study identified CsWRKY71, a transcription factor mediated the regulation of gibberellin on theanine synthesis in tea plants. CsWRKY71 was localized in the nucleus and had a typical WRKY domain. It was a member of class IIC sub- and its expression was significantly suppressed following exogenous GA3 treatment. Further assay such as EMSA, dual luciferase and asODN interfering demonstrated that CsWRKY71 significantly interacted with the promoter of CsTSI, which inhibited theanine synthesis by binding to the cis-acting element (C/T)TGAC(T/C) of CsTSI promoter. Overall, the addition of exogenous gibberellin alleviated the inhibition of CsTSI by down-regulating the expression of CsWRKY71, ultimately facilitated the rapid biosynthesis of theanine. This study elucidated the molecular mechanism of CsWRKY71 mediated gibberellin regulation of theanine synthesis in tea plant. The findings not only enhance our understanding of the regulatory processes involved in theanine synthesis in tea plants, but also provide important references for maintaining the characteristics of high theanine in tea plant.

Competitive network of polyamines metabolic and ethylene biosynthesis pathways during gibberellin-induced parthenocarpic grape fruit setting

Polyamines (PAs) and ethylene are involved in the modulation of plant growth and development. However, their roles in fruit-set, especially in exogenous gibberellin (GA3)-induced grape parthenocarpic berries, and the related competitive action mode are poorly understood. For this, we, here performed their content determination, bioinformatics and expression pattern analysis of genes to identify the key ones in the competitive network of polyamines metabolic and ethylene biosynthesis (PMEB) pathways. The content of putrescine (Put) significantly increased; while 1-aminocyclopropanecarboxylic acid (ACC) sharply decreased during the fruit-set process of GA3-induced grape parthenocarpic seedless berries. Totally, twenty-five genes in PMEB pathways, including 20 polyamines metabolic (PM) genes and 5 ethylene biosynthesis (EB) ones were identified in grape, of which 8 PM and 2 EB genes possessed the motifs responsive to phytohormone GA. The expression levels of most PMEB genes kept changing during grape fruit-set generating a competitive action mode of GA3-mediated two metabolic fluxes toward PAs and ethylene synthesis. Exogenous GA3 might enhance grape fruit-set of parthenocarpic berries via up-regulation of VvSAMS4, VvSAMDC1/2, VvODC1, VvSPDS1, and VvPAO1 to promote PAs accumulation, whereby repressing the ethylene synthesis by down-regulation of VvACS1 and VvACO2. Our findings provide novel insights into GA3-mediated competitive inhibition of ethylene by PAs to promote the fruit-set of parthenocarpic berries in grape, which has important implications for molecular breeding of seedless grape with high fruit-setting rate.

Physiological response of microalga Dunaliella parva when treated with MeJA, GA3.

DpAP2 is a transcription factor regulating carotenoid biosynthesis pathway. It was speculated that MeJA significantly decreased expression of DpAP2 gene, then the decreasing DpAP2 expression significantly inhibited expression of some key enzyme genes such as PSY, PDS and GGPS in carotenoid biosynthesis pathway. In contrast, it was speculated that GA3 significantly increased expression of DpAP2 gene, then the increasing DpAP2 expression significantly increased expression of some key enzyme genes such as PDS and GGPS in carotenoid biosynthesis pathway. To increase the content of carotenoid, we evaluated the effect of DpAP2 overexpression on carotenoid accumulation in D. parva. Transgenic D. parva showed a higher carotenoid content (3.18 mg/g DW) compared with control group (2.13 mg/g DW) at 9 d. The dosage effects of exogenous hormones MeJA and GA3 were found in D. parva cells treated with different concentrations of MeJA (10, 20, 50, 100 μM) and GA3 (10, 20, 50, 100 μM). The high concentrations of MeJA (10-100 μM) inhibited the accumulation of carotenoid, and the relative expression of DpAP2, PSY, PDS and GGPS decreased significantly. On the contrary, the relative expression of DpAP2, PDS and GGPS increased significantly when D. parva was treated with 10, 20, 50 and 100 μM GA3, which promoted the biosynthesis of carotenoid. Therefore, we inferred that there was a hierarchical regulation from hormone, transcription factor, key enzyme gene to carotenoid accumulation in carotenoid biosynthesis. Carotenoid biosynthesis was enhanced by DpAP2 overexpression (1.4930 fold of control) and exogenous substances such as GA3 (1.5889 fold of control), which laid a foundation for massive accumulation of carotenoids in microalgae. In the future, further studies were required to demonstrate the complex regulatory network.

Tendril length is determined by gibberellin deactivation during thigmo response in cucumber.

Changes in plant morphology due to mechanical stimulation are known as thigmo responses. As climbing organs in plants, tendrils can sense mechanical stimulation after attaching to a support and then change their morphology within a short time. Here, the thigmo responses of cucumber tendril were investigated. Our results showed that mechanical stimulation stopped tendril elongation and that tendril length was determined by the distance from the support in cucumber. The mimicry touch treatment indicated that mechanical stimulation stopped tendril elongation by inhibiting cell expansion. RNA-seq data showed that three gibberellin (GA) metabolic genes (CsGA2ox3, CsCYP714A2, and CsCYP714A3) were upregulated in mechanically stimulated tendrils, and a major endogenous bio-active GA (GA4) was reduced in mechanically stimulated tendrils. The roles of CsGA2ox3, CsCYP714A2, and CsCYP714A3 in GA deactivation were confirmed by their overexpression in transgenic Arabidopsis. Moreover, exogenous GA treatment recovered tendril elongation under mechanical stimulation, whereas exogenous uniconazole treatment inhibited tendril elongation without mechanical stimulation, suggesting that mechanical stimulation stopped tendril elongation, depending on GA deactivation. In summary, our results suggest that GA deactivation plays an important role in tendril thigmo response, ensuring that tendrils obtain a suitable final length according to their distance from the support in cucumber.

Inflorescence development in female cannabis plants is mediated by photoperiod and gibberellin.

In cannabis seedlings, the initiation of solitary flowers is photoperiod-independent. However, when cannabis reaches the adult stage, short-day photoperiod (SD) triggers branching of the shoot apex and a reduction in internode length, leading to development of a condensed inflorescence. We demonstrate that SD affects cannabis plants in two distinct phases: the first includes rapid elongation of the internodes and main stem, and occurring from Day 5 to Day 10 of plant cultivation under SD; in the second phase, elongation of newly developed internodes ceases, and a condensed inflorescence is formed. Exposure of plants to alternating photoperiods revealed that inflorescence onset requires at least three consecutive days of SD, and SD is consistently required throughout inflorescence maturation to support its typical condensed architecture. This photoperiod-dependent morphogenesis was associated with a decrease in gibberellin (GA4) and auxin levels in the shoot apex. Reverting the plants to a long-day photoperiod (LD) increased GA4 and auxin levels, leading to inflorescence disassembly, internode elongation, and subsequent resumption of LD growth patterns. Similar developmental patterns were observed under SD following the application of exogenous GA (and not auxin), which also impeded inflorescence development. Nevertheless, additional studies will help to further evaluate auxin's role in these developmental changes. We propose a crucial role for GA in sexual reproduction and inflorescence development in female cannabis by mediating photoperiod signaling in the inflorescence tissues.

The crosstalk interaction of ethylene, gibberellins, and arbuscular mycorrhiza improves growth in salinized tomato plants by modulating the hormonal balance

Ethylene (ET) and gibberellins (GAs) play key roles in controlling the biotic and abiotic interactions between plants and environment. To gain insights about the role of ET and GAs interactions in the mycorrization and response to salinity of tomato (Solanum lycopersicum L.) plants, the ET-insensitive (Never-ripe, Nr), and the ET-overproducer (Epinastic, Epi) mutants and their wild type cv. Micro-Tom (MT), were inoculated or not with the arbuscular mycorrhizal fungi (AMF) Rhizophagus irregularis and exposed to control (0 mM NaCl) and salinity (100 mM NaCl) conditions, with and without gibberellic acid (10−6 M GA3) application during four weeks. Exogenous GA3 enhanced plant growth irrespective of the genotype, AMF, and salinity conditions, while an additional effect on growth by AMF was only found in the ET-overproducer (Epi) mutant under control and salinity conditions. Epi almost doubled the AMF colonization level under both conditions but was the most affected by salinity and GA3 application compared to MT and Nr. In contrast, Nr registered the lowest AMF colonization level, but GA3 produced a positive effect, particularly under salinity, with the highest leaf growth recovery. Foliar GA3 application increased the endogenous concentration of GA1, GA3, and total GAs, more intensively in AMF-Epi plants, where induced levels of the ET-precursor ACC were also found. Interestingly, GA4 which is associated with AMF colonization, registered the strongest genotype x GA x AMF × salinity interactions. The different growth responses in relation to those interactions are discussed.

The effect of exogenous gibberellin and its synthesis inhibitor treatments for morphological and physiological characteristics of Tartary buckwheat

Gibberellin (GA3) is an important plant hormone involved in many physiological and developmental processes in plants. However, the physiological mechanism of GA3 on the regulation yield and grain shell thickness of Tartary buckwheat is still unclear. In this study, the thick-shelled cultivar “Jinqiao 2” and thin-shelled cultivar “Miku 18” were used to study the effects of different concentrations (0, 50, and 100 mg L−1) of exogenous GA3 and chlorocholine chloride (CCC, GA3 synthesis inhibitor) on the cellulose content, amylase, and sucrose synthase (SS) activity in grain shell and the yield of Tartary buckwheat. The application of exogenous GA3 can improve the cellulose content and the activity of amylase and SS in the grain shell of the two Tartary buckwheat varieties. It can also increase the main stem node number, main stem branch number, grains per plant, and yield. Compared with the control treatment (CK, 0 mg L−1), the 100 mg/L exogenous GA3 treatment increased the number of grains per plant, grain weight per plant, 1000-grain weight, and yield of Jinqiao 2 by 20.1%, 41.9%, 13%, and 34.7%, respectively. These items of Miku 18 were increased by 26%, 15.2%, 10.2%, and 23.8%. The application of CCC reduced the activity of amylase and SS and cellulose content in grain shell. In addition, it decreased the main stem node number, main stem branch number, grains per plant, and yield of Tartary buckwheat. In summary, exogenous GA3 treatment not only improved the yield of Tartary buckwheat but also increased the thickness of grain shell by enhancing the activity of amylase and SS and promoting the synthesis and accumulation of cellulose. The results can provide theoretical references for clarifying the physiological mechanism of the difference in shell thickness between Tartary buckwheat varieties.

Quantitative Proteomics Analysis of ABA- and GA3-Treated Malbec Berries Reveals Insights into H2O2 Scavenging and Anthocyanin Dynamics.

Abscisic acid (ABA) and gibberellic acid (GA3) are regulators of fruit color and sugar levels, and the application of these hormones is a common practice in commercial vineyards dedicated to the production of table grapes. However, the effects of exogenous ABA and GA3 on wine cultivars remain unclear. We investigated the impact of ABA and GA3 application on Malbec grapevine berries across three developmental stages. We found similar patterns of berry total anthocyanin accumulation induced by both treatments, closely associated with berry H2O2 levels. Quantitative proteomics from berry skins revealed that ABA and GA3 positively modulated antioxidant defense proteins, mitigating H2O2. Consequently, proteins involved in phenylpropanoid biosynthesis were downregulated, leading to decreased anthocyanin content at the almost ripe stage, particularly petunidin-3-G and peonidin-3-G. Additionally, we noted increased levels of the non-anthocyanins E-viniferin and quercetin in the treated berries, which may enhance H2O2 scavenging at the almost ripe stage. Using a linear mixed-effects model, we found statistical significance for fixed effects including the berry H2O2 and sugar contents, demonstrating their roles in anthocyanin accumulation. In conclusion, our findings suggest a common molecular mechanism by which ABA and GA3 influence berry H2O2 content, ultimately impacting anthocyanin dynamics during ripening.

NADP-malic Enzyme OsNADP-ME2 Modulates Plant Height Involving in Gibberellin Signaling in Rice

Plants NADP-malic enzymes (NADP-MEs) act as a class of oxidative decarboxylase to mediate malic acid metabolism in organisms. Despite NADP-MEs have been demonstrated to play pivotal roles in regulating diverse biological processes, the role of NADP-MEs involving in plant growth and development remains rarely known. Here, we characterized the function of rice cytosolic OsNADP-ME2 in regulating plant height. The results showed that RNAi silencing and knock-out of OsNADP-ME2 in rice results in a dwarf plant structure, associating with significant expression inhibition of genes involving in phytohormone Gibberellin (GA) biosynthesis and signaling transduction, but with up-regulation for the expression of GA signaling suppressor SLR1. The accumulation of major bioactive GA1, GA4 and GA7 are evidently altered in RNAi lines, and exogenous GA treatment compromises the dwarf phenotype of OsNADP-ME2 RNAi lines. RNAi silencing of OsNADP-ME2 also causes the reduction of NADP-ME activity associating with decreased production of pyruvate. Thus, our data revealed a novel function of plant NADP-MEs in modulation of rice plant height through regulating bioactive GAs accumulation and GA signaling, and provided a valuable gene resource for rice plant architecture improvement.

Exogenous GA3 Enhances Nitrogen Uptake and Metabolism under Low Nitrate Conditions in 'Duli' (Pyrus betulifolia Bunge) Seedlings.

'Duli' (Pyrus betulifolia Bunge) is one of the main rootstocks of pear trees in China. Gibberellin (GA) is a key plant hormone and the roles of GA in nitrate (NO3-) uptake and metabolism in plants remain unclear. In this study, we investigated the effects of exogenous GA3 on the N metabolism of 'Duli' seedlings under NO3- deficiency. The results showed that exogenous GA3 significantly improves 'Duli' growth under NO3- deficiency. On the one hand, GA3 altered the root architecture, increased the content of endogenous hormones (GA3, IAA, and ZR), and enhanced photosynthesis; on the other hand, it enhanced the activities of N-metabolizing enzymes and the accumulation of N, and increased the expression levels of N absorption (PbNRT2) and the metabolism genes (PbNR, PbGILE, PbGS, and PbGOGAT). However, GA3 did not delay the degradation of chlorophyll. Paclobutrazol had the opposite effect on growth. Overall, GA3 can increase NO3- uptake and metabolism and relieve the growth inhibition of 'Duli' seedlings under NO3- deficiency.

Sorbitol mediates age-dependent changes in apple plant growth strategy through gibberellin signaling.

Plants experience various age-dependent changes during juvenile to adult vegetative phase. However, the regulatory mechanisms orchestrating the changes remain largely unknown in apple (Malus domestica). This study showed that tissue-cultured apple plants at juvenile, transition, and adult phase exhibit age-dependent changes in their plant growth, photosynthetic performance, hormone levels, and carbon distribution. Moreover, this study identified an age-dependent gene, sorbitol dehydrogenase (MdSDH1), a key enzyme for sorbitol catabolism, highly expressed in the juvenile phase in apple. Silencing MdSDH1 in apple significantly decreased the plant growth and GA3 levels. However, exogenous GA3 rescued the reduced plant growth phenotype of TRV-MdSDH1. Biochemical analysis revealed that MdSPL1 interacts with MdWRKY24 and synergistically enhance the repression of MdSPL1 and MdWRKY24 on MdSDH1, thereby promoting sorbitol accumulation during vegetative phase change. Exogenous sorbitol application indicated that sorbitol promotes the transcription of MdSPL1 and MdWRKY24. Notably, MdSPL1-MdWRKY24 module functions as key repressor to regulate GA-responsive gene, Gibberellic Acid-Stimulated Arabidopsis (MdGASA1) expression, thereby leading to a shift from the quick to the slow-growth strategy. These results reveal the pivotal role of sorbitol in controlling apple plant growth, thereby improving our understanding of vegetative phase change in apple.

Effects of exogenous GA, IAA, ABA and ethylene on pear (Pyrus pyrifolia) fruit during different development stages

Effects of exogenous GA, IAA, ABA and ethylene on pear (Pyrus pyrifolia) fruit during different development stages

Comparative transcriptome analysis reveals the potential mechanism of GA3-induced dormancy release in Suaeda glauca black seeds.

Suaeda glauca Bunge produces dimorphic seeds on the same plant, with brown seeds displaying non-dormant characteristics and black seeds exhibiting intermediate physiological dormancy traits. Previous studies have shown that black seeds have a very low germination rate under natural conditions, but exogenous GA3 effectively enhanced the germination rate of black seeds. However, the physiological and molecular mechanisms underlying the effects of GA3 on S. glauca black seeds are still unclear. In this study, transcriptomic profiles of seeds at different germination stages with and without GA3 treatment were analyzed and compared, and the TTF, H2O2, O2 -, starch, and soluble sugar contents of the corresponding seed samples were determined. The results indicated that exogenous GA3 treatment significantly increased seed vigor, H2O2, and O2 - contents but decreased starch and soluble sugar contents of S. glauca black seeds during seed dormancy release. RNA-seq results showed that a total of 1136 DEGs were identified in three comparison groups and were involved mainly in plant hormone signal transduction, diterpenoid biosynthesis, flavonoid biosynthesis, phenylpropanoid biosynthesis, and carbohydrate metabolism pathway. Among them, the DEGs related to diterpenoid biosynthesis (SgGA3ox1, SgKAO and SgGA2ox8) and ABA signal transduction (SgPP2Cs) could play important roles during seed dormancy release. Most genes involved in phenylpropanoid biosynthesis were activated under GA3 treatment conditions, especially many SgPER genes encoding peroxidase. In addition, exogenous GA3 treatment also significantly enhanced the expression of genes involved in flavonoid synthesis, which might be beneficial to seed dormancy release. In accordance with the decline in starch and soluble sugar contents, 15 genes involved in carbohydrate metabolism were significantly up-regulated during GA3-induced dormancy release, such as SgBAM, SgHXK2, and SgAGLU, etc. In a word, exogenous GA3 effectively increased the germination rate and seed vigor of S. glauca black seeds by mediating the metabolic process or signal transduction of plant hormones, phenylpropanoid and flavonoid biosynthesis, and carbohydrate metabolism processes. Our results provide novel insights into the transcriptional regulation mechanism of exogenous GA3 on the dormancy release of S. glauca black seeds. The candidate genes identified in this study may be further studied and used to enrich our knowledge of seed dormancy and germination.

Identification and characterization of CsERECTA, a major gene controlling stem elongation through regulating GA biosynthesis in cucumber.

Dwarfing is an ideal agronomic trait in crop breeding, which can improve lodging resistance and increase crop productivity. In this study, we identified a dwarf mutant cp-3 from an EMS-mutagenized population, which had extremely short internodes, and the cell length and number of internodes were significantly reduced. Meanwhile, exogenous GA3 treatment partially rescued the plant height of the cp-3. Inheritance analysis showed that the cp-3 mutant was regulated via a recessive nuclear locus. A candidate gene, CsERECTA, encoding an LRR receptor-like serine/threonine-protein kinase, was cloned through a map-based cloning strategy. Sequence analysis showed that a nucleotide mutation (C ~ T) in exon 26 of CsERECTA led to premature termination of the protein. Subsequently, two transgenic lines were generated using the CRISPR/Cas9 system, and they showed plant dwarfing. Plant endogenous hormones quantitative and RNA-sequencing analysis revealed that GA3 content and the expression levels of genes related to GA biosynthesis were significantly reduced in Cser knockout mutants. Meanwhile, exogenous GA3 treatment partially rescued the dwarf phenotype of Cser knockout mutants. These findings revealed that CsERECTA controls stem elongation by regulating GA biosynthesis in cucumber.

Proteomic characterization of the different stages of seed germination in Cupressus gigantea

Abstract Seed germination is a pivotal period of plant growth and development. This process can be divided into four major stages, swelling absorption, seed coat dehiscence, radicle emergence and radicle elongation. Cupressus gigantea, a tree native to Tibet, China, is characterized by its resistance to stresses such as cold, and drought, and has a high economic and ecological value. Nevertheless, given its unique geographic location, its seeds are difficult to germinate. Therefore, it is crucial to explore the mechanisms involved in seed germination in this species to improve the germination efficiency of its seeds, thereby protecting this high-quality resource. Here, our findings indicate that seed germination was enhanced when exposed to a 6-h/8-h light/dark photoperiod, coupled with a temperature of 20°C. Furthermore, the application of exogenous GA3 (1 mg/ml, about 2.9 mM) stimulated the germination of C. gigantea seeds. Subsequently, proteomics was used to detect changes in protein expression during the four stages of seed germination. We identified 34 differentially expressed proteins (DEPs), including 13 at the radicle pre-emergence stage, and 17 at the radicle elongation stage. These DEPs were classified into eight functional groups, cytoskeletal proteins, energy metabolism, membrane transport, stress response, molecular chaperones, amino acid metabolism, antioxidant system and ABA signalling pathway. Most of them were found to be closely associated with amino acid metabolism. Combined, these findings indicate that, along with temperature and light, exogenous GA3 can increase the germination efficiency of C. gigantea seeds. Our study also offers insights into the changes in protein expression patterns in C. gigantea seeds during germination.

Two FT genes synergistically regulate the reproductive transition of loquat

Unlike annual flowering plants that exhibit a single reproductive cycle encompassing vegetative growth, flowering, and senescence within a single year, perennial woody trees undergo a transition between vegetative and reproductive growth every year after a long juvenile phase. Most woody fruit trees bloom when it turns warm in spring, and the fruit ripens in summer or autumn. However, as a member of the Maloideae subfamily, the loquat tree blooms in the cold autumn and winter, and the fruit matures in the spring. To explore the regulatory mechanism of loquat flowering, we characterized two FLOWERING LOCUS T homologous genes in loquat, EjFT1 and EjFT2. qRT-PCR results revealed that EjFT1 and EjFT2 exhibited nearly opposite expression patterns in various tissues. EjFT1 was mainly expressed in young tissues; EjFT2 was mainly expressed in mature leaves, open flowers, and fruits. EjFT2 exhibited an obvious circadian rhythm and was regulated by EjCO. After the trees were exposed to short-day conditions or sprayed with exogenous GA3, the expression of EjFT2 was strongly inhibited, and the loquat tree did not produce floral buds. Furthermore, the yeast two-hybrid, bimolecular fluorescence complementation, and Dual-luciferase assay experiments revealed that both EjFT1 and EjFT2 interacted with EjFD, with the EjFT2-EjFD protein complex enhancing the activity of EjAP1-1 and EjAP1-2 promoters, while EjFT1-EjFD inhibited the activity of the EjAP1-1 promoter. Protein structural analysis of EjFT1 and EjFT2 suggested that differences in amino acid residues at Val123/Leu123, Ser157/Ala157, and Val158/Ala158 may be the reason for their functional differences. Our results showed that EjFT1 and EjFT2 may cooperatively regulate the floral bud differentiation of loquat by competitively binding with EjFD. EjFT2 regulates the onset of loquat floral bud differentiation by responding to photoperiod and gibberellin signals, while EjFT1 is involved in the vegetative growth of loquat. These findings provide important clues for the investigation of the regulatory mechanism of loquat flowering and advance the exploration into the multiple roles of FT homologous genes in regulating the reproductive transformation and vegetative growth of flowering plants.

Exogenous Gibberellic Acid Ameliorates Chilling Injury in Peach (Prunus persica L.) by Improving the Antioxidant System

Currently, several studies have demonstrated that cold stress can cause the accumulation of reactive oxygen species (ROS) in fruit. However, little is known about the roles of gibberellic acid (GA3) on the antioxidant system in the mitochondria of fruit. To explore the molecular basis of GA3 interference with the chilling tolerance of fruit, ‘Jinqiuhongmi’ peach fruit was treated with 0.1 mmol L−1 GA3 after harvest. Exogenous GA3 treatment relieved the chilling injury of postharvest peach fruit with a lower cold injury index and higher antioxidant level. In addition, GA3 delayed the senescence of peaches by reducing the firmness, respiratory action, and ethylene production. The antioxidant enzyme activities were elevated, including superoxide dismutase (SOD) and catalase (CAT). Moreover, GA3-treated peaches exhibited lower hydrogen peroxide (H2O2) and malondialdehyde (MDA) in comparison with the control. These results showed that the application of 0.1 mmol L−1 of GA3 enhanced the chilling resistance of peach fruit by regulating the antioxidant system.