Responses of PYR/PYL/RCAR ABA Receptors to Contrasting stresses, Heat and Cold in Arabidopsis

Comprehensive Transcriptomic and Physiological Insights into the Response of Root Growth Dynamics During the Germination of Diverse Sesame Varieties to Heat Stress

Heat stress constitutes a serious threat to sesame (Sesamum indicum L.). Root development during seed germination plays an essential role in plant growth and development. Nevertheless, the regulatory mechanisms underlying heat stress remain poorly understood. In this study, two sesame varieties differing in leaf heat tolerance (Zheng Taizhi 3 (heat-tolerant) and SP19 (heat-sensitive)) have been employed to investigate the impact of heat stress on root growth during germination. The results showed that heat stress significantly reduced the radicle length by 35.71% and 67.02% in Zheng Taizhi 3 and SP19, respectively, while germination rates remained unchanged. In addition, heat stress induced oxidative stress, as evidenced by increased reactive oxygen species (ROS) production, malondialdehyde (MDA) content, and reduced indole-3-acetic acid (IAA) content, accompanied by enhanced antioxidant enzyme activities, including those of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and the abscisic acid (ABA) content significantly increased in both varieties. However, the oxidation resistance in the roots of Zheng Taizhi 3 was enhanced compared to that of SP19 under heat stress, while IAA production was maintained and ABA content was reduced. A comparative transcriptome analysis identified 6164 and 6933 differentially expressed genes (DEGs) in Zheng Taizhi 3 and SP19, respectively, with 4346 overlapping DEGs. These DEGs included those related to stress tolerance, such as heat-shock proteins (HSPs), the antioxidant defense system, hormone signal transduction, and the biosynthetic pathway of phenylpropanoid. These findings provide insights into the physiological and molecular mechanisms underlying the adaptation of sesame to heat stress, which could inform breeding strategies for developing heat-tolerant sesame varieties.

Genome-wide characterization of pyrabactin resistance 1-like (PYL) family genes revealed AhPYL6 confer the resistance to Ralstonia solanacearum in peanut

Bacterial wilt (BW) caused by Ralstonia solanacearum severely impacts the yield and quality of peanut (Arachis hypogaea L.), a globally cultivated industrial crop. Despite the abscisic acid (ABA) signaling pathway have been identified as key factors in peanut resistance to BW, the molecular mechanism remains unclear. Through systematic identification, it was discovered that the peanut genome contains 18 ABA receptor pyrabactin resistance 1-like (PYL) family genes, which show conservation with other plant species. Among these PYL genes in peanut (referred to as AhPYL), AhPYL6 and AhPYL16 showed significant up-regulation in response to salicylic acid, jasmonic acid, ABA treatments, and R. solanacearum infection. Subsequently, the full-length AhPYL6 was cloned and functionally characterized. The fusion protein AhPYL6-YFP was predominantly expressed in the cytoplasm and nucleus of tobacco leaves, and overexpression of AhPYL6 notably enhanced resistance against R. solanacearum. Expression analysis revealed that the expression levels defense -related genes including NbNPR1, NbPR2, NbPR3, NbHRS203, NbEFE26, and NbNDR1 were significantly up-regulated by the overexpression of AhPYL6, which suggested that AhPYL6 confers the resistance to R. solanacearum through promoting expression of defense -related genes. These findings highlight the potential roles of PYL ABA receptors in the plant defense response to bacterial pathogens.

CmPYL7 positively regulates the cold tolerance via interacting with CmPP2C24-like in oriental melon

Pyrabactin or Actin Resistance1/PYR1-Like/Regulatory Components of abscisic acid (ABA) Receptors (PYR/PYL/RCARs, referred to as PYLs) are direct receptors of ABA that function pivotally in the ABA-signaling pathway. Previously, we discovered that CmPYL7 was strongly upregulated by cold stress in oriental melon (Cucumis melo). In this study, we demonstrated that CmPYL7 was strongly induced by cold treatment (Cold), Cold+ABA, and Cold+fluridone (Flu, an ABA inhibitor) treatments, while the expression level of CmPYL7 under Cold+Flu is lower than that of cold treatment. Silencing CmPYL7 in oriental melon seedlings significantly decreased cold tolerance due to the reduced activities of antioxidant enzymes [superoxide dismutase (SOD); catalase (CAT), and ascorbate peroxidase (APX)] and the accumulation of H2O2, accompanied by higher electrolyte leakage and MDA content, but lower proline and soluble sugar content. In contrast, overexpressing CmPYL7 in Arabidopsis plants significantly increased cold tolerance owing to the enhanced activities of antioxidant enzymes (SOD, CAT, and APX) and limited H2O2, accompanied by lower electrolyte leakage and MDA content, but higher proline and soluble sugar contents. CmPYL7 was found to interact with CmPP2C24-like in vivo and in vitro, whose expression is downregulated under cold stress. Furthermore, silenced CmPP2C24-like in oriental melon plants significantly increased cold tolerance, exhibiting lower electrolyte leakage and MDA content and higher proline and soluble sugar contents. The activities of SOD, CAT, and APX were further enhanced and contents of H2O2 were significantly limited from increasing in TRV-CmPP2C24-like seedlings. These results demonstrated that CmPYL7 functions positively in the ABA-signaling pathway to regulate cold tolerance by interacting with CmPP2C24-like protein.

The gene CmPYL6 strongly contributes to cold tolerance in oriental melon

The current simple and crude facilities make melon production more susceptible to cold stress during off-season cultivation in China. The ABA signalling pathway is an important target for breeding cold-tolerant melon. Cold-tolerant No. 330 and cold-sensitive No. 410 oriental melon genotypes were used to analyse the relationship between ABA and cold tolerance. 12 CmPYLs, ABA receptors, were identified from the melon genome database according to sequence alignment and phylogenetic analysis. Gene function of CmPYL6 in cold tolerance was analysed using VIGS in No. 330 and overexpression in Arabidopsis WT. A total of 12 CmPYL members contain the representative domain and conserved sites. Under cold treatment, No.330 seedlings had lower electrolyte leakage and MDA content, higher ABA content and CmPYL6 expression than seedlings of No. 410. Exogenous application of ABA upregulated expression of CmPYL6 and enhanced cold tolerance of both genotypes, while inhibiting ABA accumulation reduced expression of CmPYL6 and cold tolerance of both genotypes. CmPYL6-silenced No. 330 seedlings had reduced cold tolerance, increased electrolyte leakage and MDA content as well as limited proline and soluble sugar content, while CmPYL6 overexpressed transgenic Arabidopsis plants had enhanced cold tolerance, with limited electrolyte leakage and MDA content, as well as increased proline and soluble sugar content. The CmPYL6 gene is probably an important ABA receptor in regulating cold tolerance of oriental melon. Our study provides a direction for improving breeding of cold tolerance of oriental melon.

Overexpression of Potato PYL16 Gene in Tobacco Enhances the Transgenic Plant Tolerance to Drought Stress

PYR/PYL/RCAR proteins are abscisic acid (ABA) receptors that play a crucial role in plant responses to abiotic stresses. However, there have been no research reports on potato PYL so far. In this study, a potato PYL gene named StPYL16 was identified based on transcriptome data under drought stress. Molecular characteristics analysis revealed that the StPYL16 protein possesses an extremely conserved PYL family domain. The tissue expression results indicated that the StPYL16 is predominantly expressed at high levels in the underground parts, particularly in tubers. Abiotic stress response showed that StPYL16 has a significant response to drought treatment. Further research on the promoter showed that drought stress could enhance the activation activity of the StPYL16 promoter on the reporter gene. Then, transient and stable expression of StPYL16 in tobacco enhanced the drought resistance of transgenic plants, resulting in improved plant height, stem thickness, and root development. In addition, compared with wild-type plants, StPYL16 transgenic tobacco exhibited lower malondialdehyde (MDA) content, higher proline accumulation, and stronger superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities. Meanwhile, StPYL16 also up-regulated the expression levels of stress-related genes (NtSOD, NtCAT, NtPOD, NtRD29A, NtLEA5, and NtP5CS) in transgenic plants under drought treatment. These findings indicated that the StPYL16 gene plays a positive regulatory role in potato responses to drought stress.

Botrytis cinerea causes different plant responses in grape (Vitis vinifera) berries during noble and grey rot: diverse metabolism versus simple defence

The complexity of the interaction between the necrotrophic pathogen Botrytis cinerea and grape berries (Vitis vinifera spp.) can result in the formation of either the preferred noble rot (NR) or the loss-making grey rot (GR), depending on the prevailing climatic conditions. In this study, we focus on the functional gene set of V. vinifera by performing multidimensional scaling followed by differential expression and enrichment analyses. The aim of this study is to identify the differences in gene expression between grape berries in the phases of grey rot, noble rot, and developing rot (DR, in its early stages) phases. The grapevine transcriptome at the NR phase was found to exhibit significant differences from that at the DR and GR stages, which displayed strong similarities. Similarly, several plant defence-related pathways, including plant-pathogen interactions as hypersensitive plant responses were found to be enriched. The results of the analyses identified a potential plant stress response pathway (SGT1 activated hypersensitive response) that was found to be upregulated in the GR berry but downregulated in the NR berry. The study revealed a decrease in defence-related in V. vinifera genes during the NR stages, with a high degree of variability in functions, particularly in enriched pathways. This indicates that the plant is not actively defending itself against Botrytis cinerea, which is otherwise present on its surface with high biomass. This discrepancy underscores the notion that during the NR phase, the grapevine and the pathogenic fungi interact in a state of equilibrium. Conversely the initial stages of botrytis infection manifest as a virulent fungus-plant interaction, irrespective of whether the outcome is grey or noble rot.

Genome-wide identification and expression analysis of Hsp70 family genes in Cassava (Manihot esculenta Crantz)

Hsp70 proteins function as molecular chaperones, regulating various cellular processes in plants. In this study, a genome-wide analysis led to the identification of 22 Hsp70 (MeHsp70) genes in cassava. Phylogenetic relationship studies with other Malpighiales genomes (Populus trichocarpa, Ricinus communis and Salix purpurea) classified MeHsp70 proteins into eight groups (Ia, Ib, Ic, Id, Ie, If, IIa and IIb). Promoter analysis of MeHsp70 genes revealed the presence of tissue-specific, light, biotic and abiotic stress-responsive cis-regulatory elements showing their functional importance in cassava. Meta-analysis of publically available RNA-seq transcriptome datasets showed constitutive, tissue-specific, biotic and abiotic stress-specific expression patterns among MeHsp70s in cassava. Among 22 Hsp70, six MeHsp70s viz., MecHsp70-3, MecHsp70-6, MeBiP-1, MeBiP-2, MeBiP-3 and MecpHsp70-2 displayed constitutive expression, while three MecHsp70s were induced under both drought and cold stress conditions. Five MeHsp70s, MecHsp70-7, MecHsp70-11, MecHsp70-12, MecHsp70-13, and MecHsp70-14 were induced under drought stress conditions. We predicted that 19 MeHsp70 genes are under the regulation of 24 miRNAs. This comprehensive genome-wide analysis of the Hsp70 gene family in cassava provided valuable insights into their functional roles and identified various potential Hsp70 genes associated with stress tolerance and adaptation to environmental stimuli.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03760-3.

Involvement of microRNA164 in responses to heat stress in Arabidopsis

MicroRNAs (miRNAs) are considered to be integral parts of plant stress regulatory networks. Under long-term heat stress, miR164 is induced. Conversely, its targets are repressed. Transgenic overexpressors (164OE) and mutants of MIR164 (mir164) were used to study miR164's functions during heat responses. Target gene expression decreased in 164OE transgenic plants and increased in mir164a-4 and mir164b mutants. Under heat stress, the mir164 mutants presented heat-sensitive phenotypes, while 164OE transgenic plants showed better thermotolerance than wild-type (WT) plants. Overexpression of miR164 decreased heat-inhibition of hypocotyl lengths. Under heat stress, miR164 target genes modulated the expression of chlorophyll b reductase and chlorophyll catabolic genes, reducing the chlorophyll a/b ratio. More H₂O₂ accumulated in the mir164 mutants under heat stress, which may have caused oxidative damage. In addition, expression of HSPs was altered in the experimental plants compared to that of the WT. Overall, miR164 influenced target gene expression, altering development, chlorophyll a/b ratio, H₂O₂-caused damage, and HSPs expression under long-term heat stress. These phenomena, in turn, likely influence the thermotolerance of plants.

Integrated Physiological and Transcriptomic Analyses Revealed Improved Cold Tolerance in Cucumber (Cucumis sativus L.) by Exogenous Chitosan Oligosaccharide

Cucumber (Cucumis sativus L.), sensitive to cold stress, is one of the most economically important vegetables. Here, we systematically investigated the roles of exogenous glycine betaine, chitosan, and chitosan oligosaccharide in alleviating cold stress in cucumber seedlings. The results showed that 50 mg·L−1 chitosan oligosaccharide had the best activity. It effectively increases plant growth, chlorophyll content, photosynthetic capacity, osmotic regulatory substance content, and antioxidant enzyme activities while reducing relative electrical conductivity and malondialdehyde levels in cucumber seedlings under cold stress. To reveal the protective effects of chitosan oligosaccharide in cold stress, cucumber seedlings pretreated with 50 mg·L−1 chitosan oligosaccharide were sampled after 0, 3, 12, and 24 h of cold stress for transcriptome analysis, with distilled water as a control. The numbers of differentially expressed genes in the four comparison groups were 656, 1274, 1122, and 957, respectively. GO functional annotation suggested that these genes were mainly involved in “voltage-gated calcium channel activity”, “carbohydrate metabolic process”, “jasmonic acid biosynthetic”, and “auxin response” biological processes. KEGG enrichment analysis indicated that these genes performed important functions in “phenylpropanoid biosynthesis”, “MAPK signaling pathway—plant”, “phenylalanine metabolism”, and “plant hormone signal transduction.” These findings provide a theoretical basis for the use of COS to alleviate the damage caused by cold stress in plant growth and development.

Genome-wide identification and expression reveal the involvement of the FCS-like zinc finger (FLZ) gene family in Gossypium hirsutum at low temperature

FCS-like zinc finger (FLZ) is a plant-specific gene family that plays an important regulatory role in plant growth and development and its response to stress. However, studies on the characteristics and functions of cotton FLZ family genes are still lacking. This study systematically identified members of the cotton FLZ gene family based on cotton genome data. The cotton FLZ family genes were systematically analyzed by bioinformatics, and their expression patterns in different tissues and under low-temperature stress were analyzed by transcriptome and qRT-PCR. The G. hirsutum genome contains 56 FLZ genes distributed on 20 chromosomes, and most of them are located in the nucleus. According to the number and evolution analysis of FLZ family genes, FLZ family genes can be divided into five subgroups in cotton. The G. hirsutum FLZ gene has a wide range of tissue expression types, among which the expression is generally higher in roots, stems, leaves, receptacles and calyx. Through promoter analysis, it was found that it contained the most cis-acting elements related to methyl jasmonate (MeJA) and abscisic acid (ABA). Combined with the promoter and qRT-PCR results, it was speculated that GhFLZ11, GhFLZ25, GhFLZ44 and GhFLZ55 were involved in the response of cotton to low-temperature stress. Taken together, our findings suggest an important role for the FLZ gene family in the cotton response to cold stress. This study provides an important theoretical basis for further research on the function of the FLZ gene family and the molecular mechanism of the cotton response to low temperature.

Combined Transcriptome and Metabolome Profiling Provide Insights into Cold Responses in Rapeseed (Brassica napus L.) Genotypes with Contrasting Cold-Stress Sensitivity

Low temperature is a major environmental factor, which limits rapeseed (Brassica napus L.) growth, development, and productivity. So far, the physiological and molecular mechanisms of rapeseed responses to cold stress are not fully understood. Here, we explored the transcriptome and metabolome profiles of two rapeseed genotypes with contrasting cold responses, i.e., XY15 (cold-sensitive) and GX74 (cold-tolerant). The global metabolome profiling detected 545 metabolites in siliques of both genotypes before (CK) and after cold-stress treatment (LW). The contents of several sugar metabolites were affected by cold stress with the most accumulated saccharides being 3-dehydro-L-threonic acid, D-xylonic acid, inositol, D-mannose, D-fructose, D-glucose, and L-glucose. A total of 1943 and 5239 differentially expressed genes were identified from the transcriptome sequencing in XY15CK_vs_XY15LW and GX74CK_vs_GX74LW, respectively. We observed that genes enriched in sugar metabolism and biosynthesis-related pathways, photosynthesis, reactive oxygen species scavenging, phytohormone, and MAPK signaling were highly expressed in GX74LW. In addition, several genes associated with cold-tolerance-related pathways, e.g., the CBF-COR pathway and MAPK signaling, were specifically expressed in GX74LW. Contrarily, genes in the above-mentioned pathways were mostly downregulated in XY15LW. Thus, our results indicate the involvement of these pathways in the differential cold-stress responses in XY15 and GX74.

Overexpression VaPYL9 improves cold tolerance in tomato by regulating key genes in hormone signaling and antioxidant enzyme

BACKGROUND

Abscisic acid (ABA) has been reported in controlling plant growth and development, and particularly dominates a role in resistance to abiotic stress. The Pyrabactin Resistance1/PYR1-Like /Regulatory Components of ABA receptors (PYR1/PYL/RCAR) gene family, of which the PYL9 is a positive regulator related to stress response in ABA signaling transduction. Although the family has been identified in grape, detailed VaPYL9 function in cold stress remains unknown.

RESULTS

In order to explore the cold tolerance mechanism in grape, VaPYL9 was cloned from Vitis amurensis. The subcellular localization showed that VaPYL9 was mainly expressed in the plasma membrane. Yeast two-hybrid (Y2H) showed VaPCMT might be a potential interaction protein of VaPYL9. Through the overexpression of VaPYL9 in tomatoes, results indicated transgenic plants had higher antioxidant enzyme activities and proline content, lower malondialdehyde (MDA) and H₂O₂ content, and improving the ability to scavenge reactive oxygen species than wild-type (WT). Additionally, ABA content and the ratio of ABA/IAA kept a higher level than WT. Quantitative real-time PCR (qRT-PCR) showed that VaPYL9, SlNCED3, SlABI5, and antioxidant enzyme genes (POD, SOD, CAT) were up-regulated in transgenic tomatoes. Transcriptome sequencing (RNA-seq) found that VaPYL9 overexpression caused the upregulation of key genes PYR/PYL, PYL4, MAPK17/18, and WRKY in transgenic tomatoes under cold stress.

CONCLUSION

Overexpression VaPYL9 enhances cold resistance of transgenic tomatoes mediated by improving antioxidant enzymes activity, reducing membrane damages, and regulating key genes in plant hormones signaling and antioxidant enzymes.

Overexpression of grape ABA receptor gene VaPYL4 enhances tolerance to multiple abiotic stresses in Arabidopsis

BACKGROUND

Abscisic acid (ABA) plays a crucial role in abiotic stress responses. The pyrabactin resistance (PYR)/PYR-like (PYL)/regulatory component of ABA receptor (RCAR) proteins that have been characterized as ABA receptors function as the core components in ABA signaling pathway. However, the functions of grape PYL genes in response to different abiotic stresses, particularly cold stress, remain less studied.

RESULTS

In this study, we investigated the expression profiles of grape PYL genes upon cold treatment and isolated the VaPYL4 gene from Vitis amurensis, a cold-hardy grape species. Overexpression of VaPYL4 gene in grape calli and Arabidopsis resulted in enhanced cold tolerance. Moreover, plant resistance to drought and salt stress was also improved by overexpressing VaPYL4 in Arabidopsis. More importantly, we evaluated the contribution of VaPYL4 to plant growth and development after the treatment with cold, salt and drought stress simultaneously. The transgenic plants showed higher survival rates, earlier flowering phenotype, and heavier fresh weight of seedlings and siliques when compared with wild-type plants. Physiological analyses showed that transgenic plants had much lower content of malondialdehyde (MDA) and higher peroxidase (POD) activity. Stress-responsive genes such as RD29A (Responsive to desiccation 29A), COR15A (Cold responsive 15A) and KIN2 (Kinase 2) were also significantly up-regulated in VaPYL4-overexpressing Arabidopsis plants.

CONCLUSIONS

Our results show that overexpression of VaPYL4 could improve plant performance upon different abiotic stresses, which therefore provides a useful strategy for engineering future crops to deal with adverse environments.

Comparative physiological and transcriptomic analysis of sesame cultivars with different tolerance responses to heat stress

High temperature is the main factor affecting plant growth and can cause plant growth inhibition and yield reduction. Here, seedlings of two contrasting sesame varieties, i.e., Zheng Taizhi 3 (heat-tolerant) and SP19 (heat-sensitive), were treated at 43 °C for 10 days. The results showed that the relative electrical conductivity, hydrogen peroxide levels, and superoxide anion radical levels of both varieties increased significantly under high temperature stress. Additionally, dry matter accumulation and chlorophyll content decreased significantly, and the activities of peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) increased. However, under HT stress, the content of reactive oxygen species in Zheng Taizhi 3 was lower than that in SP19, and the activities of SOD, CAT, and POD as well as the chlorophyll content in Zheng Taizhi 3 were higher than those in SP19. Comparative transcriptome analysis identified 6736 differentially expressed genes (DEGs); 5526 DEGs (2878 up and 2648 down) were identified in Zheng Taizhi 3, and 5186 DEGs (2695 up and 2491 down) were identified in SP19, with 3976 overlapping DEGs. These DEGs included stress tolerance-related heat-shock proteins, as well as genes related to carbohydrate and energy metabolism, signal transduction, endoplasmic reticulum protein processing, amino acid metabolism, and secondary metabolism. Overall, our results showed that the heat tolerance of Zheng Taizhi 3 was attributed to a stronger antioxidant defense system, enabling the variety to avoid oxidative damage compared with the heat-sensitive SP19. Moreover, some specifically expressed and high-abundance genes in Zheng Taizhi 3 were involved in regulatory mechanisms related to heat tolerance, including plant hormone signal transduction and heat shock protein regulation, thereby enhancing heat tolerance. The study contributes to a deeper understanding of the underlying complex molecular mechanisms involved in the responses of sesame seedlings to heat stress and provides a potential strategy for heat-resistant new varieties.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-022-01195-3.

Exogenous melatonin improves the resistance to cucumber bacterial angular leaf spot caused by Pseudomonas syringae pv. Lachrymans

Pseudomonas syringae pv. Lachrymans (Psl) is a bacterial pathogen that causes cucumber bacterial angular leaf spot (BALS). It is known that melatonin (MT), as a pleiotropic signal molecule, can improve plant stress tolerance, but less information is available about the function of MT on plant resistance to bacteria disease. Here, we investigated the effect of MT on cucumber BALS. Our results show that MT inhibited the bacteria Psl growth significantly in vitro and attenuated cucumber BALS remarkably in vivo. The concentration of bacteria in leaves treated with 0.1 mM MT was approximately 10,000 times reduced at 5 days-post-inoculation (dpi), compared to the control without MT. Transcriptomic analysis showed that 225 differentially expressed genes (DEGs) were induced in leaves after just MT treatment for 3 h. The functions of these DEGs were mainly associated with hormone signal transduction, mitogen-activated protein kinase (MAPK) signaling pathway, and photosynthesis, suggesting that MT could regulate plant growth and induce plant immunity. Moreover, 665 DEGs were induced when leaves were treated with exogenous MT in combination with the bacteria inoculation for 12 h. The functions of these DEGs were much related to plant-pathogen interaction, hormone signal transduction, and amino acids biosynthesis pathways. Many MT-induced DEGs were involved in some distinct signal transduction pathways, such as calmodulin (CaM), polyamines (PAs), nitric oxide (NO), and salicylic acid (SA). The physiological analysis shows that exogenous MT spray reduced the stomatal aperture and enhanced the activities of antioxidant and defense enzymes, which were in consistent with the results of the transcriptome analysis. In addition, MT may function in regulating the metabolic balance between plant growth and defense. In conclusion, our results demonstrate that MT could alleviate the cucumber BALS via inhibiting propagation and invasion of Psl, activating plant signaling, enhancing antioxidative and defense systems, inducing stress-related genes expression, and regulating the plant growth-defense balance.

PYR/PYL/RCAR Receptors Play a Vital Role in the Abscisic-Acid-Dependent Responses of Plants to External or Internal Stimuli

Abscisic acid (ABA) is a phytohormone that plays a key role in regulating several developmental processes as well as in response to stressful conditions such as drought. Activation of the ABA signaling cascade allows the induction of an appropriate physiological response. The basic components of the ABA signaling pathway have been recognized and characterized in recent years. Pyrabactin resistance, pyrabactin resistance-like, and the regulatory component of ABA receptors (PYR/PYL/RCAR) are the major components responsible for the regulation of the ABA signaling pathway. Here, we review recent findings concerning the PYR/PYL/RCAR receptor structure, function, and interaction with other components of the ABA signaling pathway as well as the termination mechanism of ABA signals in plant cells. Since ABA is one of the basic elements related to abiotic stress, which is increasingly common in the era of climate changes, understanding the perception and transduction of the signal related to this phytohormone is of paramount importance in further increasing crop tolerance to various stress factors.

Transcriptome profiling of Malus sieversii under freezing stress after being cold-acclimated

Background

Freezing temperatures are an abiotic stress that has a serious impact on plant growth and development in temperate regions and even threatens plant survival. The wild apple tree (Malus sieversii) needs to undergo a cold acclimation process to enhance its freezing tolerance in winter. Changes that occur at the molecular level in response to low temperatures are poorly understood in wild apple trees.

Results

Phytohormone and physiology profiles and transcriptome analysis were used to elaborate on the dynamic response mechanism. We determined that JA, IAA, and ABA accumulated in the cold acclimation stage and decreased during freezing stress in response to freezing stress. To elucidate the molecular mechanisms of freezing stress after cold acclimation, we employed single molecular real-time (SMRT) and RNA-seq technologies to study genome-wide expression profiles in wild apple. Using the PacBio and Illumina platform, we obtained 20.79G subreads. These reads were assembled into 61,908 transcripts, and 24,716 differentially expressed transcripts were obtained. Among them, 4410 transcripts were differentially expressed during the whole process of freezing stress, and these were examined for enrichment via GO and KEGG analyses. Pathway analysis indicated that “plant hormone signal transduction”, “starch and sucrose metabolism”, “peroxisome” and “photosynthesis” might play a vital role in wild apple responses to freezing stress. Furthermore, the transcription factors DREB1/CBF, MYC2, WRKY70, WRKY71, MYB4 and MYB88 were strongly induced during the whole stress period.

Conclusions

Our study presents a global survey of the transcriptome profiles of wild apple trees in dynamic response to freezing stress after two days cold acclimation and provides insights into the molecular mechanisms of freezing adaptation of wild apple plants for the first time. The study also provides valuable information for further research on the antifreezing reaction mechanism and genetic improvement of M. sieversii after cold acclimation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07998-0.

What if the cold days return? Epigenetic mechanisms in plants to cold tolerance

The epigenetic could be an important, but seldom assessed, mechanisms in plants inhabiting cold ecosystems. Thus, this review could help to fill a gap in the current literature. Low temperatures are one of the most critical environmental conditions that negatively affect the growth, development, and geographic distribution of plants. Exposure to low temperatures results in a suit of physiological, biochemical and molecular modifications through the reprogramming of the expression of genes and transcription factors. Scientific evidence shows that the average annual temperature has increased in recent years worldwide, with cold ecosystems (polar and high mountain) being among the most sensitive to these changes. However, scientific evidence also indicates that there would be specific events of low temperatures, due it is highly relevant to know the capacity for adaptation, regulation and epigenetic memory in the face of these events, by plants. Epigenetic regulation has been described to play an important role in the face of environmental stimuli, especially in response to abiotic stress. Several studies on epigenetic mechanisms have focused on responses to stress as drought and/or salinity; however, there is a gap in the current literature considering those related to low temperatures. In this review, we focus on systematizing the information published to date, related to the regulation of epigenetic mechanisms such as DNA methylation, histone modification, and non-coding RNA-dependent silencing mechanisms, in the face of plant´s stress due to low temperatures. Finally, we present a schematic model about the potential responses by plants taking in count their epigenetic memory; considering a global warming scenario and with the presence or absence of extreme specific events of low temperatures.

Heat stress in Marchantia polymorpha: Sensing and mechanisms underlying a dynamic response

Sensing and response to high temperatures are crucial to prevent heat-related damage and to preserve cellular and metabolic functions. The response to heat stress is a complex and coordinated process that involves several subcellular compartments and multi-level regulatory networks that are synchronized to avoid cell damage while maintaining cellular homeostasis. In this review, we provide an insight into the most recent advances in elucidating the molecular mechanisms involved in heat stress sensing and response in Marchantia polymorpha. Based on the signaling pathways and genes that were identified in Marchantia, our analyses indicate that although with specific particularities, the core components of the heat stress response seem conserved in bryophytes and angiosperms. Liverworts not only constitute a powerful tool to study heat stress response and signaling pathways during plant evolution, but also provide key and simple mechanisms to cope with extreme temperatures. Given the increasing prevalence of high temperatures around the world as a result of global warming, this knowledge provides a new set of molecular tools with potential agronomical applications.

Atmospheric pressure plasma treatment induces abscisic acid production, reduces stomatal aperture and improves seedling growth in Arabidopsis thaliana

Cold atmospheric pressure plasmas (CAPPs) have been widely used for pre-sowing treatment in agriculture to accelerate seed germination; however, information on their application to pre-transplant seedlings is scarce. The roles of the phytohormone abscisic acid (ABA) on guard cell aperture that control air exchange with the environment were investigated after CAPPs treatment. In this study, Arabidopsis thaliana seedling growth was evaluated under CAPPs treatment at different doses. Besides, the optimal growth stimulation dose was selected to further evaluate changes in ABA, ROS, Ca²⁺ and stomatal aperture during growth .The expression of most ABA signalling genes were aslo examined to investigate the mechanism. CAPPs treatment for 1 min significantly promoted Arabidopsis seedling growth; the ABA concentration in seedlings increased and peaked 48 h after treatment but was lower than in the control after 96 h. Transcript levels of most ABA signalling genes were markedly enhanced at 48 h, although their transcripts were significantly downregulated after 96 h. CAPPs treatment also reduced stomatal aperture after 24 h and accelerated ROS accumulation in guard cells. The Ca²⁺ concentration in the treatment group was markedly higher than in the control at 24 and 96 h. The results suggest that CAPPs treatment accelerates ABA accumulation in Arabidopsis at early growth stages and ABA regulates ROS and Ca²⁺ concentrations to affect stomatal aperture, and both ABA and stoma size are affected in CAPPs stimulation of Arabidopsis seedling growth.