Journal of Plant Growth Regulation最新文献

High sensitivity and rapid closure of wheat stomata to environmental stimuli make it difficult and inconvenient when investigating stomatal physiology and morphology using epidermal peels. This is due to inevitable mechanical stress to stomatal guard cells when separating epidermis from mesophyll cells, which induced a vast majority of stomatal closure in wheat. Stomata are more open and active in detached leaves than in epidermal peels. Based on these observations, we proposed a simple method, which promotes stomatal opening using detached leaves rather than epidermis for physiological observations. Stomatal response to stimuli was significantly increased when using intact leaf segment. The method was used to investigate stomatal behaviours of two wheat genotypes with contrasting salt tolerance to salinity stress. The effects of salt stress and exogenous abscisic acid (ABA) treatment on stomatal behaviours were also assessed. The salt-tolerant genotype, H-135, demonstrated a greater stomatal closure rate than the salt-sensitive genotype, H-093, in response to exogenous ABA under salt stress, highlighting the potential of stomatal responsiveness as an indicator for breeding salt-resistant crops. This method not only facilitates the effective initiation of stomatal opening but also ensures the continued responsiveness of stomata to subsequent treatments in wheat.

This study aims to investigate the molecular mechanisms governing bolting in spinach (Spinacia oleracea) by analyzing gene expression patterns in key regulatory pathways. Two cultivars, Kashan (early bolting) and Virofly (late-bolting), were analyzed using quantitative real-time polymerase chain reaction (qRT-PCR) at different developmental stages. The photoperiod pathway genes Cryptochrome2 (CRY2) and Flavin-binding kelch repeat F-box protein (FKF1) showed distinct expression dynamics, highlighting their roles in the vegetative-to-reproductive transition. Aging pathway genes Topless (TPL), Squamosa promoter binding protein5 (SPL5), SPL15, and Alpha-ketoglutarate-dependent dioxygenase AlkB-like (AlkB) revealed complex expression patterns, with SPL5 and SPL15 differing significantly in Virofly. Circadian pathway genes LATE ELONGATED HYPOCOTYL (LHY) and TIMING OF CAB EXPRESSION 1 (TOC1) showed distinct patterns, particularly LHY in Kashan. Autonomous pathway genes LUMINIDEPENDENS (LD) and FLOWERING LOCUS D (FLD) also varied, with LD higher in Kashan at the eight-leaf stage, while FLD was generally elevated. These findings provide insights into the interactions among photoperiod, aging, circadian, and autonomous pathways, suggesting regulatory mechanisms influencing bolting time. Further research into these pathways could enhance spinach breeding for improved yield and quality.

Wall-associated protein kinases (WAKs), as one subfamily of the receptor-like protein kinases (RLKs) in plants, have been shown to be required for multiple biological processes including cell elongation regulation. However, little information is available about the roles of plant WAKs in root morphogenesis regulation. Here, a rice WAK subfamily member, OsWAK12, was isolated and confirmed to be involved in root morphogenesis regulation. OsWAK12 is mainly highly expressed in both young and mature roots in rice. Phenotypic analysis showed that the Cas9-edited mutants of OsWAK12 exhibited a shorter primary root, shorter root hair length and less root hair density at seedling stage than wild type Nipponbare. Moreover, OsWAK12 overexpression in rice displays reverse phenotypes compared to these results of the Cas9-edited mutants of OsWAK12. Further analysis revealed that OsWAK12 expression was significantly induced by the auxin indoleacetic acid (IAA) and the sensitivity of primary root and root hairs to IAA and endogenous IAA content were altered in the Cas9-edited and overexpression mutants of OsWAK12. The sensitivity of the Cas9-edited mutants of OsWAK12 to IAA was decreased, contrary to the results of its overexpression mutants. Summarily, these results suggest that OsWAK12 plays important roles in rice root morphogenesis via the auxin pathway.

Salt-tolerant microbes are known to mitigate various biotic and abiotic stresses in plants. However, the intimate mechanisms involved, as well as their effects on the production of signaling molecules associated with the host plant–microbe interaction remain largely unknown. The present work aimed to investigate the role and potential uses of arbuscular mycorrhizal fungi (AMF) Rhizophagus intraradices and/or halotolerant plant growth-promoting rhizobacteria (PGPR) Bacillus subtilis in improving plant growth, functional biochemical synthesis and signaling of endogenous abscisic acid during plant response to short- and long-term salt stress in the forage halophyte Sulla carnosa. Plant growth attributes and biochemical traits were determined at 2 different time intervals (45 and 60 d after transplanting time) when salinity was raised from 100 to 200 mM NaCl. S. carnosa showed significant reduction in dry biomass in response to NaCl stress at the second harvest (200 mM NaCl); however inoculating plants with B. subtilis alone or associated with R. intraradices offset salt impact. Leaf electrolyte leakage was significantly increased by salinity but was significantly reduced following dual microbial inoculation. The applied bacterial inoculants also mitigated oxidative stress as reflected by the higher activities of catalase (APX) and superoxide dismutase (SOD) antioxidant enzymes and reduced H₂O₂ level. Inoculation with B. subtilis and R. intraradices upregulated 9-cisepoxycarotenoid dioxygenase 1 (NCED1) and SOD genes expression in S. carnosa plants upon salinity treatment. Furthermore, dual AMF-PGPR -inoculated plants accumulated significantly higher levels of abscisic acid (ABA) in both leaves and roots than non-inoculated and single inoculated plants under salinity stress at both harvest times, thereby accounting for their higher salt tolerance of salt-challenged S. carnosa plants. As a whole, the use of halophytic plants associated with beneficial soil microorganisms could improve the effectiveness of biological methods for saline soil rehabilitation. At the mechanistic level, ABA might represent a key player in the attenuation of salt impact in inoculated plants.

The effect of salt stress was evaluated on putative mutant seedlings of three polyembryonic mango genotypes viz., Bappakkai, Nekkare, and Kurukkan. Imposition of salinity stress resulted in a decrease in chlorophyll content, relative water content, and gas exchange parameters while enhancing the levels of stress markers like Na⁺/K⁺ ratio, total phenols, and proline. In total, thirteen phenolic acid compounds were identified including eight hydroxybenzoic acids and five hydroxycinnamic acids wherein hydroxybenzoic acid (majorly gallic acid) comprised more than 99% of total phenolic acids. In all the three genotypes, the concentration of protocatechuic acid, 2, 4-Dihydroxy benzoic acid, gallic acid, chlorogenic acid, and t-cinnamic acid increased with increasing level of salt stress indicating their potential role in mango salt tolerance. Bappakkai recorded higher K⁺, highest fold increase in proline content (+ 7.27 fold), highest percent increase in chlorogenic acid (+ 510%), protocatechuic acid (+ 750%), and ferulic acid along with lower Na⁺/K⁺ ratio and lower reduction in the levels of caffeic and sinapic acid at higher level of salt stress suggesting that putative mutants of Bappakkai were better at tolerating salt stress as compared to the other two genotypes. Exogenous application of ferulic acid (FA) to Nekkare putative mutants increased the activity of enzymatic antioxidants, superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). Further, quantitative real-time PCR analysis also revealed higher expression levels of SOD, CAT, and APX in FA-treated Nekkare mutants under salinity stress. The results of this study besides identifying distinct phenolic acid signatures in response to stresses like gamma irradiation and salinity, also confirm the potential of physical mutagenesis in breeding salt-tolerant rootstocks in mango.

Drought and altered nutrient dynamics are aggravated by anthropic actions, especially in semiarid environments, such as Brazilian Seasonally Dry Tropical Forests (Caatinga). However, it is not known how nutrient levels affect growth and biochemical responses in plants present in the Caatinga under drought. The aim of this study was to evaluate morphological and biochemical responses in Pavonia varians (native species with medicinal potential) and Megathyrsus maximus (invasive exotic species used in cattle feeding) present in the Caatinga with the application of nitrogen, phosphorus and potassium (NPK) under water restriction and rehydration. The experiment was conducted in a greenhouse with seedlings collected from the Catimbau National Park (Pernambuco, Brazil) in a factorial design with NPK application and water regimes. Plants were harvested after water restriction and after rehydration. NPK application improved the responses of P. varians to water restriction, increasing the leaf dry weight, total N, total K, and proline content. Additionally, MDA and H₂O₂ levels decreased in P. varians under water restriction with NPK application. In contrast, M. maximus without NPK application under water restriction increased SOD and CAT enzyme activities and decreased MDA levels. After rehydration, both species exhibited growth recovery. NPK application in P. varians increased the total K and total soluble carbohydrate contents, while M. maximus increased the number of leaves and root dry weight. Species have different mechanisms for combating drought stress, especially non-enzymatically through proline. Nutritional treatment with pre-stress NPK was an effective alternative against oxidative damage, especially for the native species P. varians.

Under light with a low proportion of far-red (FR) light, plants perceive themselves as growing in open places, which may lead them to increase leaf hydraulic conductance (K_leaf) to cope with the higher water demand associated with increased light intensities. We evaluated K_leaf of cucumber (Cucumis sativus L.) seedlings that had been acclimatized to light with different proportions of FR. K_leaf tended to increase with decreasing FR light. K_leaf and leaf vein length density were positively correlated, indicating that increased K_leaf caused by low FR light may have been caused by changes in leaf vein structure. To clarify whether acclimatization to low-FR light can improve tolerance to high evaporative demand, we evaluated changes in stomatal conductance (g_s), quantum yield of photosystem II (Φ_PSII), and leaf water potential (Ψ_leaf) when seedlings that had been acclimatized to light with FR light in the same proportion as sunlight (FR+) or light without FR light (FR−) were transferred to a high vapor-pressure deficit (VPD) condition. After transfer to high VPD, g_s and Ψ_leaf of the seedlings decreased in all treatment groups, but the decrease was smaller in the FR− seedlings. After transfer to high VPD, Φ_PSII decreased significantly in the FR+ seedlings, but not in the FR− seedlings. These findings suggest that the changes in stress tolerance induced by FR light may be partly mediated by changes in K_leaf. Our results also indicate a potential new technique for mitigating drought stress in horticultural crops by controlling FR light.

Human or natural activities have made the rhizosphere prone to heavy metal (loid) stresses that involve the fluctuating dynamics of mineral-nutrient translocation in plants. To control the nutrient deficiency and growth of plants, the use of plant hormones and vitamins can effectively mediate the reverse effects of crops grown in As-contaminated soils. The current trial was managed to reverse the toxic sequels of As-stress with foliar application of 0.03 mM of indole-3-acetic acid (I3A) and 250 mg/L of vitamin B1 (Vit.B1) in maize (Zea mays L.) cultivars (cv. Pearl and cv. Akbar) under diverse As- levels (50, 100 mg/kg). Applied As-stress (100 mg/kg) increased As-levels in shoot (119.23-fold, 126.38-fold), and root (82.03-fold, 90.69-fold), while Vit.B1 and I3A combined application reduced the As-uptake in shoot (1.66-fold, 1.31-fold) and root (2.05-fold, 1.33-fold), respectively, of cv. Akbar and cv. Pearl under As-level (100 mg/kg). Furthermore, combined application of Vit.B1and I3A significantly increased the uptake of shoot minerals; potassium (59.7, 55.33%), calcium (30, 28.5%), phosphorus (80.86, 70.37%), nitrogen (32.52, 29.87%), ferrous (50.71, 34.81%), manganese (8.41, 2.26%), and seed oil physicochemical properties such as oil saponification values (42.15, 61.35%), iodine values (40.96, 38.52%), refractive index (42.67, 29. 45%),while decreasing the oil unsponifiable values (39.32, 24.49%), para-ansidine values (22.39, 16.52%), oil density (16.36, 14.16%) and oil free fatty acids (38.10, 35.98%), respectively, of cv. Pearl and cv. Akbar under As-stress level (100 mg/kg). Overall outcomes encourage the application of Vit.B1 and I3A in enhancing the nutrient uptake and seed oil quality in maize to counter As-stress. However, much investigation is still required, and open field trials should be managed to unveil the putative role of Vit.B1 and I3A at the molecular level.

Fruit ripening is a complex physiological and metabolic process regulated by plant hormones. The ripening of climacteric fruits is accompanied by softening, especially ‘Nanguo’ pear. The importance of ethylene in fruit softening is well established; however, an understanding of its effects during the later stages of fruit development requires further investigation. In this study, ethylene was sprayed on ‘Nanguo’ pear fruits before harvest resulting in enhanced fruit quality by increasing the soluble solid and sugar contents while decreasing the stone cell content. Additionally, ethylene promoted the activities of polygalacturonase, pectin methylesterase, cellulase, and β-galactosidase enzymes that play a critical role in cell wall metabolism, by up-regulating PuPG and PuPG2 expression. This leaded to changes in the cell wall structure and breakdown of its components, a reduction of cellulose and original pectin content, and an increase in water-soluble pectin content. These results indicate that ethylene enhances fruit softening by up-regulating the expression of genes involved in cell wall metabolism to facilitate the activity of cell wall degrading enzymes.

Sheath rot of rice is one of the most devastating diseases of rice due to its ability to reduce the yield significantly in all rice cultivating areas of India. The purpose of this study was to assess the effectiveness of Bacillus cereus strain RBS-57 against sheath rot disease of rice. In addition, it enables us to understand the molecular mechanism of the host–pathogen-bioagent interactions using a proteomic approach. A combination of seed treatment, seedling dip, and foliar spray with RBS-57 liquid formulation has recorded the lowest sheath rot disease index, both under pot experiment (21.33%) and field conditions (15.33% in trial I and 12.42% in trial II, respectively). In addition to that, RBS-57 application enhanced the plant growth and yield attributes. Moreover, a 2D-PAGE study uses protein profiling to illustrate the molecular response of the tripartite interaction between host–pathogen-bioagent. MALDI-TOF mass spectrometry (MS/MS) analysis identified a total of 20 differentially expressed proteins, primarily implicated in plant metabolism and development, defense response, transcription and signalling. Selected genes were validated by quantitative Real-Time PCR (qRT-PCR) analysis. The alterations in protein abundance and transcripts were positively correlated for all the genes. The present study provides initial insights into the molecular mechanism that underlies the tripartite interaction between the host–pathogen-bioagent in rice plants.