Functions In Stress Tolerance Research Articles

In Silico Identification and Characterization of Rare Cold Inducible 2 (RCI2) Gene Family in Cotton.

RCI2/PMP3s are involved in biotic and abiotic stresses and have an influence on the regulation of many genes. RCI2/PMP3 genes, which particularly encode small membrane proteins of the PMP3 family, are involved in abiotic stress responses in plants. In this work, in silico studies were used to investigate RCI2's potential function in stress tolerance and organogenesis. We conducted an extensive study of the RCI2 gene family and revealed 36 RCI2 genes from cotton species that were distributed over 36 chromosomes of the cotton genome. Functional and phylogenetic examination of the RCI2/PMP3 gene family has been studied in Arabidopsis, but in cotton, the RCI2/PMP3 genes have not yet been studied. Phylogenetic and sequencing studies revealed that cotton RCI2s are conserved, with most of them categorized into six distinct clades. A chromosome distribution and localization study indicated that cotton RCI2 genes were distributed unevenly on 36 chromosomes with segmental duplications, suggesting that the cotton RCI2 family is evolutionarily conserved. Many cis-elements related to stress responsiveness, development, and hormone responsiveness were detected in the promoter regions of the cotton RCI2. Moreover, the 36 cotton RCI2s revealed tissue-specific expression patterns in the development of cotton performed by transcriptome analysis. Gene structure analysis indicated that nearly all RCI2 genes have two exons and one intron. All of the cotton RCI2 genes were highly sensitive to drought, abscisic acid, salt, and cold treatments, demonstrating that they may be employed as genetic objects to produce stress-resistant plants.

Heat shock protein TaHSP17.4, a TaHOP interactor in wheat, improves plant stress tolerance

Adaptation to drought and salt stresses is a fundamental part of plant cell physiology and is of great significance for crop production under environmental stress. Heat shock proteins (HSPs) are molecular chaperones that play a crucial role in folding, assembling, translocating, and degrading proteins. However, their underlying mechanisms and functions in stress tolerance remain elusive. Here, we identified the HSP TaHSP17.4 in wheat by analyzing the heat stress-induced transcriptome. Further analysis showed that TaHSP17.4 was significantly induced under drought, salt, and heat stress treatments. Intriguingly, yeast-two-hybrid analysis showed that TaHSP17.4 interacts with the HSP70/HSP90 organizing protein (HOP) TaHOP, which plays a significant role in linking HSP70 and HSP90. We found that TaHSP17.4- and TaHOP-overexpressing plants have a higher proline content and a lower malondialdehyde content than wild-type plants under stress conditions and display strong tolerance to drought, salt, and heat stress. Additionally, qRT-PCR analysis showed that stress-responsive genes relevant to reactive oxygen species scavenging and abscisic acid signaling pathways were significantly induced in TaHSP17.4- and TaHOP-overexpressing plants under stress conditions. Together, our findings provide insight into HSP functions in wheat and two novel candidate genes for improvement of wheat varieties.

Golgi-localized MORN1 promotes lipid droplet abundance and enhances tolerance to multiple stresses in Arabidopsis.

Lipid droplet (LD) in vegetative tissues has recently been implicated in environmental responses in plants, but its regulation and its function in stress tolerance are not well understood. Here, we identified a Membrane Occupation and Recognition Nexus 1 (MORN1) gene as a contributor to natural variations of stress tolerance through genome-wide association study in Arabidopsis thaliana. Characterization of its loss-of-function mutant and natural variants revealed that the MORN1 gene is a positive regulator of plant growth, disease resistance, cold tolerance, and heat tolerance. The MORN1 protein is associated with the Golgi and is also partly associated with LD. Protein truncations that disrupt these associations abolished the biological function of the MORN1 protein. Furthermore, the MORN1 gene is a positive regulator of LD abundance, and its role in LD number regulation and stress tolerance is highly linked. Therefore, this study identifies MORN1 as a positive regulator of LD abundance and a contributor to natural variations of stress tolerance. It implicates a potential involvement of Golgi in LD biogenesis and strongly suggests a contribution of LD to diverse processes of plant growth and stress responses.

Genome-wide survey and expression analysis of Dof transcription factor family in sweetpotato shed light on their promising functions in stress tolerance.

DNA-binding with one finger (Dof) transcription factors play a crucial role in plant abiotic stress regulatory networks, although massive Dofs have been systematically characterized in plants, they have not been identified in the hexaploid crop sweetpotato. Herein, 43 IbDof genes were detected to be disproportionally dispersed across 14 of the 15 chromosomes of sweetpotato, and segmental duplications were discovered to be the major driving force for the expansion of IbDofs. The collinearity analysis of IbDofs with their related orthologs from eight plants revealed the potential evolutionary history of Dof gene family. Phylogenetic analysis displayed that IbDof proteins were assigned into nine subfamilies, and the regularity of gene structures and conserved motifs was consistent with the subgroup classification. Additionally, five chosen IbDof genes were shown to be substantially and variably induced under various abiotic conditions (salt, drought, heat, and cold), as well as hormone treatments (ABA and SA), according to their transcriptome data and qRT-PCR experiments. Consistently, the promoters of IbDofs contained a number of cis-acting elements associated with hormone and stress responses. Besides, it was noted that IbDof2 had transactivation activity in yeasts, while IbDof-11/-16/-36 did not, and protein interaction network analysis and yeast two-hybrid experiments revealed a complicated interaction connection amongst IbDofs. Collectively, these data lay a foundation for further functional explorations of IbDof genes, especially with regards to the possible application of multiple IbDof members in breeding the tolerant plants.

Plant Peroxisomal Polyamine Oxidase: A Ubiquitous Enzyme Involved in Abiotic Stress Tolerance.

Polyamines (PAs) are positively charged amines that are present in all organisms. In addition to their functions specific to growth and development, they are involved in responding to various biotic and abiotic stress tolerance functions. The appropriate concentration of PA in the cell is maintained by a delicate balance between the catabolism and anabolism of PAs, which is primarily driven by two enzymes, namely diamine oxidase and polyamine oxidase (PAO). PAOs have been found to be localized in multiple subcellular locations, including peroxisomes. This paper presents a holistic account of peroxisomal PAOs. PAOs are flavin adenine dinucleotide-dependent enzymes with varying degrees of substrate specificity. They are expressed differentially upon various abiotic stress conditions, namely heat, cold, salinity, and dehydration. It has also been observed that in a particular species, the various PAO isoforms are expressed differentially with a spatial and temporal distinction. PAOs are targeted to peroxisome via a peroxisomal targeting signal (PTS) type 1. We conducted an extensive bioinformatics analysis of PTS1s present in various peroxisomal PAOs and present a consensus peroxisome targeting signal present in PAOs. Furthermore, we also propose an evolutionary perspective of peroxisomal PAOs. PAOs localized in plant peroxisomes are of potential importance in abiotic stress tolerance since peroxisomes are one of the nodal centers of reactive oxygen species (ROS) homeostasis and an increase in ROS is a major indicator of the plant being in stress conditions; hence, in the future, PAO enzymes could be used as a key candidate for generating abiotic stress tolerant crops.

The ScAPD1-like gene from the desert moss Syntrichia caninervis enhances resistance to Verticillium dahliae via phenylpropanoid gene regulation.

Soloist is a member of a distinct and small subfamily within the AP2/ERF transcriptional factor family that play important roles in plant biotic and abiotic stress responses. There are limited studies of Soloist genes and their functions are poorly understood. We characterized the abiotic and biotic stress tolerance function of the ScSoloist gene (designated as ScAPD1-like) from the desert moss Syntrichia caninervis. ScAPD1-like responded to multiple abiotic, biotic stresses and plant hormone treatments. ScAPD1-like protein located to the nucleus and bound to several DNA elements. Overexpression of ScAPD1-like in Arabidopsis did not alter abiotic stress resistance or inhibit Pseudomonas syringae pv. tomato (Pst) DC3000 infection. However, overexpression of ScAPD1-like significantly increased the resistance of transgenic Arabidopsis and S. caninervis to Verticillium dahliae infection, decreased reactive oxygen species accumulation and improved reactive oxygen species scavenging activity. ScAPD1-like overexpression plants altered the abundance of transcripts for lignin synthesis and promoted lignin accumulation in Arabidopsis. ScAPD1-like directly bind to RAV1, AC elements, and TATA-box in the promoters of AtPAL1 and AtC4H genes, respectively, invitro. Chromatin immunoprecipitation-quantitative polymerase chain reaction assays demonstrated ScAPD1-like directly bound to PAL and C4H genes promoters in Arabidopsis and their homologs in S. caninervis. In S. caninervis, ScAPD1-like overexpression and RNAi directly regulated the abundance of ScPAL and ScC4H transcripts and modified the metabolites of phenylpropanoid pathway. We provide insight into the function of Soloist in plant defense mechanisms that likely occurs through activation of the phenylpropanoid biosynthesis pathway. ScAPD1-like is a promising candidate gene for breeding strategies to improve resistance to Verticillium wilt.

Genome-wide identification and comprehensive analysis of tubby-like protein gene family in multiple crops.

The highly conserved tubby-like proteins (TLPs) play key roles in animal neuronal development and plant growth. The abiotic stress tolerance function of TLPs has been widely explored in plants, however, little is known about comparative studies of TLPs within crops. Bioinformatic identification, phylogenetic analysis, Cis-element analysis, expression analysis, Cis-element analysis, expression analysis and so on were explored to analysis the TLP gene family of multiple crops. In this study, a comprehensive analysis of TLP genes were carried out in seven crops to explore whether similar function of TLPs in rice could be achieved in other crops. We identified 20, 9, 14, 11, 12, 35, 14 and 13 TLP genes in Glycine max, Hordeum vulgare, Sorghum bicolor, Arabidopsis thaliana, Oryza sativa Japonica, Triticum aestivum, Setaria italic and Zea mays, respectively. All of them were divided into two groups and ten orthogroups (Ors) based on amino acids. A majority of TLP genes had two domains, tubby-like domain and F-box domain, while members of Or5 only had tubby-like domain. In addition, Or5 had more exons and shorter DNA sequences, showing that characteristics of different Ors reflected the differentiated function and feature of TLP genes in evolutionary process, and Or5 was the most different from the other Ors. Besides, we recognized 25 cis-elements in the promoter of TLP genes and explored multiple new regulation pathway of TLPs including light and hormone response. The bioinformatic and transcriptomic analysis implied the stresses induced expression and possible functional redundancy of TLP genes. We detected the expression level of 6 OsTLP genes at 1 to 6 days after seed germination in rice, and the most obvious changes in these days were appeared in OsTLP10 and OsTLP12. Combined yeast two-hybrid system and pull down assay, we suggested that the TLP genes of Or1 may have similar function during seed germination in different species. In general, the results of comprehensive analysis of TLP gene family in multiple species provide valuable evolutionary and functional information of TLP gene family which are useful for further application and study of TLP genes.

Integration of Metabolomics and Transcriptomics Reveal the Mechanism Underlying Accumulation of Flavonols in Albino Tea Leaves

Albino tea plants (Camellia sinensis) have been reported to possess highly inhibited metabolism of flavonoids compared to regular green tea leaves, which improves the quality of the tea made from these leaves. However, the mechanisms underlying the metabolism of catechins and flavonols in albino tea leaves have not been well elucidated. In this study, we analyzed a time series of leaf samples in the greening process from albino to green in a thermosensitive leaf-color tea mutant using metabolomics and transcriptomics. The total content of polyphenols dramatically decreased, while flavonols (such as rutin) were highly accumulated in albino leaves compared to in green leaves. After treatment with increasing environment temperature, total polyphenols and catechins were increased in albino mutant tea leaves; however, flavonols (especially ortho-dihydroxylated B-rings such as rutin) were decreased. Meanwhile, weighted gene co-expression network analysis of RNA-seq data suggested that the accumulation of flavonols was highly correlated with genes related to reactive oxygen species scavenging. Histochemical localization further demonstrated that this specific accumulation of flavonols might be related to their biological functions in stress tolerance. These findings suggest that the temperature-stimulated accumulation of total polyphenols and catechins in albino mutant tea leaves was highly induced by enhanced photosynthesis and accumulation of its products, while the initial accumulation and temperature inhibition of flavonols in albino mutant tea leaves were associated with metabolism related to oxidative stress. In conclusion, our results indicate that the biosynthesis of flavonoids could be driven by many different factors, including antioxidation and carbon skeleton storage, under favorable and unfavorable circumstances, respectively. This work provides new insights into the drivers of flavonoid biosynthesis in albino tea leaves, which will further help to increase tea quality by improving cultivation measures.

H2S improves salt‐stress recovery via organic acid turn‐over in apple seedlings

Signalling roles of hydrogen sulphide (H2 S) in stress biology are widely reported but not sufficiently established to urge its use in agronomic practice. Our lack of quantitative understanding of the metabolic rewiring in H2 S signalling makes it difficult to elucidate its functions in stress tolerance on the biochemical level. Here, Malus hupehensis Rehd. var. pingyiensis seedlingswere first treated with salt stress for 2 weeks and then treated with four different concentrations of NaHS. Through vigorous investigations, including phenotypic analysis, 13 C transient labellingand targeted metabolic and transcriptomic analysis, for the first time in the seedlings of a woody fruit crop, we found out that H2 S recycles fixed carbons through glycolysis and tricarboxylic acid cycle to inhibit the futile accumulation of carbohydrates, to maintain an efficient CO2 assimilation, to keep abalanced starch metabolism, to produce sufficient H2 O2 , to maintain malate/γ-aminobutyric acid homeostasis via an H2 O2 -induced anion channel (aluminium-activated malate transporter)and eventually to improve salt-stress recovery. Our results systematically demonstrate the vital roles of central carbon metabolism in H2 S signalling and clarify the mode of action of H2 S in apple seedlings. We conclude that H2 S signalling interacts with central carbon metabolism in a bottom-up manner to recover plant growth after salt stress.

Coordinated regulation of TORC2 signaling by MCC/eisosome-associated proteins, Pil1 and tetraspan membrane proteins during the stress response.

MCCs are linear invaginations of the yeast plasma membrane that form stable membrane microdomains. Although over 20 proteins are localized in the MCCs, it is not well understood how these proteins coordinately maintain normal MCC function. Pil1 is a core eisosome protein and is responsible for MCC-invaginated structures. In addition, six-tetraspan membrane proteins (6-Tsp) are localized in the MCCs and classified into two families, the Sur7 family and Nce102 family. To understand the coordinated function of these MCC proteins, single and multiple deletion mutants of Pil1 and 6-Tsp were generated and their MCC structure and growth under various stresses were investigated. Genetic interaction analysis revealed that the Sur7 family and Nce102 function in stress tolerance and normal eisosome assembly, respectively, by cooperating with Pil1. To further understand the role of MCCs/eisosomes in stress tolerance, we screened for suppressor mutants using the SDS-sensitive phenotype of pil1Δ 6-tspΔ cells. This revealed that SDS sensitivity is caused by hyperactivation of Tor kinase complex 2 (TORC2)-Ypk1 signaling. Interestingly, inhibition of sphingolipid metabolism, a well-known downstream pathway of TORC2-Ypk1 signaling, did not rescue the SDS-sensitivity of pil1Δ 6-tspΔ cells. These results suggest that Pil1 and 6-Tsp cooperatively regulate TORC2 signaling during the stress response.

Convergence of sphingolipid desaturation across over 500 million years of plant evolution.

For plants, acclimation to low temperatures is fundamental to survival. This process involves the modification of lipids to maintain membrane fluidity. We previously identified a new cold-induced putative desaturase in Physcomitrium (Physcomitrella) patens. Lipid profiles of null mutants of this gene lack sphingolipids containing monounsaturated C24 fatty acids, classifying the new protein as sphingolipid fatty acid denaturase (PpSFD). PpSFD mutants showed a cold-sensitive phenotype as well as higher susceptibility to the oomycete Pythium, assigning functions in stress tolerance for PpSFD. Ectopic expression of PpSFD in the Atads2.1 (acyl coenzyme A desaturase-like 2) Arabidopsis thaliana mutant functionally complemented its cold-sensitive phenotype. While these two enzymes catalyse a similar reaction, their evolutionary origin is clearly different since AtADS2 is a methyl-end desaturase whereas PpSFD is a cytochrome b5 fusion desaturase. Altogether, we suggest that adjustment of membrane fluidity evolved independently in mosses and seed plants, which diverged more than 500 million years ago.

Overexpression of the ThTPS gene enhanced salt and osmotic stress tolerance in Tamarix hispida

Trehalose is a non-reducing disaccharide with high stability and strong water absorption properties that can improve the resistance of organisms to various abiotic stresses. Trehalose-6-phosphate synthase (TPS) plays important roles in trehalose metabolism and signaling. In this study, the full-length cDNA of ThTPS was cloned from Tamarix hispida Willd. A phylogenetic tree including ThTPS and 11 AtTPS genes from Arabidopsis indicated that the ThTPS protein had a close evolutionary relationship with AtTPS7. However, the function of AtTPS7 has not been determined. To analyze the abiotic stress tolerance function of ThTPS, the expression of ThTPS in T. hispida under salt and drought stress and JA, ABA and GA3 hormone stimulation was monitored by qRT-PCR. The results show that ThTPS expression was clearly induced by all five of these treatments at one or more times, and salt stress caused particularly strong induction of ThTPS in the roots of T. hispida. The ThTPS gene was transiently overexpressed in T. hispida. Both physiological indexes and staining results showed that ThTPS gene overexpression increased salt and osmotic stress tolerance in T. hispida. Overall, the ThTPS gene can respond to abiotic stresses such as salt and drought, and its overexpression can significantly improve salt and osmotic tolerance. These findings establish a foundation to better understand the responses of TPS genes to abiotic stress in plants.

The GATA Gene Family in Chickpea: Structure Analysis and Transcriptional Responses to Abscisic Acid and Dehydration Treatments Revealed Potential Genes Involved in Drought Adaptation

The GATA transcription factors are important transcriptional regulators of plant growth and responses to environmental stimuli. Here, a total of 25 CaGATA genes was identified in chickpea (Cicer arietinum), and their basic characteristics, including gene structure, duplication patterns, conserved domains and various physical and chemical parameters were subsequently determined. Of our interest, the enrichment of the hormone- and stress-responsive cis-regulatory elements in the promoters of CaGATA genes has been analyzed to predict the CaGATA members with potential hormone-mediated functions in stress tolerance. Furthermore, the tissue-specific expression patterns of the CaGATA genes were assessed using the available transcriptome data. More importantly, transcript levels of the identified CaGATA genes were quantified in roots and leaves of chickpea seedlings exposed to ABA (abscisic acid) or dehydration treatment using real-time quantitative PCR. Expression levels of a total of 12 CaGATA genes were significantly altered in roots and/or leaves by both ABA and dehydration treatments, suggesting that these genes might play roles in regulation of chickpea response to water stress in an ABA-dependent manner. Out of these genes, only CaGATA04 was induced in both roots and leaves by ABA and dehydration treatments. Furthermore, CaGATA05 and 21 were the most highly induced in roots (8.55-fold) and leaves (4.90-fold), respectively, by dehydration. Findings of this study have provided important insights into the CaGATA family of chickpea, as well as useful information for selection of CaGATA genes of interest for in-depth functional characterizations that might lead to development of chickpea cultivars with improved performance under water-deficit conditions.

Functional compensation dominates the assembly of plant rhizospheric bacterial community

Plant rhizosphere microbes play a key role in plant-soil feedbacks. However, the intrinsic principles governing the assembly of the rhizosphere microbial community remain unclear. To understand these principles, we studied the taxonomical and functional characteristics of the reassembled maize rhizosphere bacterial communities after transplanting between soils. The composition of the rhizosphere bacterial community was measured by high-throughput amplicon-based Illumina MiSeq sequencing of the V4 region of the 16S ribosomal RNA (rRNA) gene. The rhizosphere functional profile was assessed using 16S rRNA data in the PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved State) software. We found that the reassembled rhizosphere bacterial community was recruited from both soil and endosphere communities. The assembly and functional traits of the rhizosphere bacterial community were associated with the concentrations of soil available nutrients. The most important rhizospheric functions were to improve host stress tolerance, followed by nutrient cycling functions. The rhizosphere bacterial taxa that improved host stress tolerance were in low abundance and were primarily derived from the surrounding bulk soil. Moreover, the rhizosphere nutrient cycling functions were marginalized in nutrient-excessive soils. Plants may sacrifice stress tolerance functions and enhance compensatory colonization of nutrient cycling-related endophytes in the rhizosphere in nutrient-deficient soils. Our results demonstrate that the levels of soil available nutrients mediate the assembly of rhizosphere bacterial communities to satisfy plant-required functions. This assembly principle is useful for manipulating the bacterial communities of plant roots to improve agricultural sustainability.

A 2-Cys peroxiredoxin gene from Tamarix hispida improved salt stress tolerance in plants

BackgroundPeroxiredoxins (Prxs) are a large family of antioxidant enzymes that respond to biotic and abiotic stress by decomposing reactive oxygen species (ROS). In this study, the stress tolerance function of the Th2CysPrx gene was further analysed. It lays a foundation for further studies on the salt tolerance molecular mechanism of T. hispida and improved salt tolerance via transgenic plants.ResultsIn this study, the stress tolerance function of the Th2CysPrx gene was further analysed. The results of transgenic tobacco showed higher seed germination rates, root lengths, and fresh weight under salt stress than wild-type tobacco. Simultaneously, physiological indicators of transgenic tobacco and T. hispida showed that Th2CysPrx improved the activities of antioxidant enzymes and enhanced ROS removal ability to decrease cellular damage under salt stress. Moreover, Th2CysPrx improved the expression levels of four antioxidant genes (ThGSTZ1, ThGPX, ThSOD and ThPOD).ConclusionsOverall, these results suggested that Th2CysPrx enhanced the salt tolerance of the transgenic plants. These findings lay a foundation for further studies on the salt tolerance molecular mechanism of T. hispida and improved salt tolerance via transgenic plants.

Transgenic expression of carbonic anhydrase III in cardiac muscle demonstrates a mechanism to tolerate acidosis.

Carbonic anhydrase III (CAIII) is abundant in liver, adipocytes, and skeletal muscles, but not heart. A cytosolic enzyme that catalyzes conversions between CO2 and in the regulation of intracellular pH, its physiological role in myocytes is not fully understood. Mouse skeletal muscles lacking CAIII showed lower intracellular pH during fatigue, suggesting its function in stress tolerance. We created transgenic mice expressing CAIII in cardiomyocytes that lack endogenous CAIII. The transgenic mice showed normal cardiac development and life span under nonstress conditions. Studies of ex vivo working hearts under normal and acidotic conditions demonstrated that the transgenic and wild-type mouse hearts had similar pumping functions under normal pH. At acidotic pH, however, CAIII transgenic mouse hearts showed significantly less decrease in cardiac function than that of wild-type control as shown by higher ventricular pressure development, systolic and diastolic velocities, and stroke volume via elongating the time of diastolic ejection. In addition to the effect of introducing CAIII into cardiomyocytes on maintaining homeostasis to counter acidotic stress, the results demonstrate the role of carbonic anhydrases in maintaining intracellular pH in muscle cells as a potential mechanism to treat heart failure.

Sweetpotato bZIP Transcription Factor IbABF4 Confers Tolerance to Multiple Abiotic Stresses.

The abscisic acid (ABA)-responsive element binding factors (ABFs) play important regulatory roles in multiple abiotic stresses responses. However, information on the stress tolerance functions of ABF genes in sweetpotato (Ipomoea batatas [L.] Lam) remains limited. In the present study, we isolated and functionally characterized the sweetpotato IbABF4 gene, which encodes an abiotic stress-inducible basic leucine zipper (bZIP) transcription factor. Sequence analysis showed that the IbABF4 protein contains a typical bZIP domain and five conserved Ser/Thr kinase phosphorylation sites (RXXS/T). The IbABF4 gene was constitutively expressed in leaf, petiole, stem, and root, with the highest expression in storage root body. Expression of IbABF4 was induced by ABA and several environmental stresses including drought, salt, and heat shock. The IbABF4 protein localized to the nucleus, exhibited transcriptional activation activity, and showed binding to the cis-acting ABA-responsive element (ABRE) in vitro. Overexpression of IbABF4 in Arabidopsis thaliana not only increased ABA sensitivity but also enhanced drought and salt stress tolerance. Furthermore, transgenic sweetpotato plants (hereafter referred to as SA plants) overexpressing IbABF4, generated in this study, exhibited increased tolerance to drought, salt, and oxidative stresses on the whole plant level. This phenotype was associated with higher photosynthetic efficiency and lower malondialdehyde and hydrogen peroxide content. Levels of endogenous ABA content and ABA/stress-responsive gene expression were significantly upregulated in transgenic Arabidopsis and sweetpotato plants compared with wild-type plants under drought stress. Our results suggest that the expression of IbABF4 in Arabidopsis and sweetpotato enhances tolerance to multiple abiotic stresses through the ABA signaling pathway.

Molecular characterization of a sweet potato stress tolerance-associated trehalose-6-phosphate synthase 1 gene (IbTPS1) in response to abiotic stress

Trehalose-6-phosphate synthase (TPS) plays an important regulatory role in the response of plants to multiple abiotic stresses. However, our knowledge of the stress tolerance functions of TPS genes in sweet potato (Ipomoea batatas [L.] Lam) remains limited. In the present study, we isolated and functionally characterized the sweet potato gene encoding TPS1, IbTPS1. Sequence analysis showed that IbTPS1 belongs to class I TPS proteins and harbors highly conserved acceptor (glucose-6-phosphate [Glc6P]) and donor (uridine diphosphoglucose [UDP-Glc]) binding sites. The IbTPS1 gene showed the highest level of constitutive expression in leaves and storage roots of sweet potato plants and was induced by several environmental stresses including drought, salt, and heat shock. The IbTPS1 protein might be localized to the cytosol. Complementation assay of yeast tps1Δ and tps1Δtps2Δ growth-defective mutants confirmed the TPS activity of IbTPS1, and truncation of the N-terminal extension of IbTPS1 (ΔNIbTPS1) increased the catalytic activity of the protein. Additionally, expression of IbTPS1 in yeast conferred abiotic stress tolerance to dehydration, salinity, and oxidation, and expression of ΔNIbTPS1 further enhanced the tolerance to abiotic stresses. The results of this study advance our understanding of the functions of IbTPS1 under abiotic stress conditions. Our results suggest that the IbTPS1 gene is an excellent candidate for improving the stress tolerance of different crop plants.

Isolation, expression and function analysis of a bZIP transcription factor IbbZIP37 in sweetpotato (Ipomoea batatas L. [Lam

bZIP transcription factor play an important regulatory role in the response to multiple abiotic stresses. However, our knowledge of the stress tolerance functions of bZIP family genes in sweetpotato (Ipomoea batatas [L.] Lam) remains limited. In the present study, we isolated and functionally characterized an IbbZIP37 gene encoding an abiotic stress-inducible bZIP group A transcription factor. Sequence analysis showed that the IbbZIP37 contained a typical bZIP domain and five conserved Ser/Thr kinase phosphorylation sites (RXXS/T). The IbbZIP37 protein was localized in the nucleus and possessed transcriptional activation activity. The results of electrophoretic mobility shift assays indicated that IbbZIP37 can bind to the ABRE cis-element, not do to DRE cis-element in vitro. The IbbZIP37 gene showed the highest level of constitutive expression in root, especially in fibrous root and storage root body. Gene expression was induced by ABA and several environmental stresses including drought, salt and heat shock. Our results suggest that IbbZIP37 is a positive transcription regulator of the abiotic stresses response, which can be used as an excellent candidate for improving the stress tolerance of different crop plants.

Genome-Wide Identification and Expression Analysis of the Cytidine Deaminase Subfamily in Rice

Cytidine deaminase (CDA) belongs to the subfamily of cytidine deaminase-like family of proteins, which is involved in the nucleotide metabolism. As CDAs participate in stress response and disease resistance processes, especially as RNA editing enzymes, they are deemed to play vital roles in variety of biological processes. Considering that the reports of the exact functions of CDAs are obscure and rare, it is necessary to study the CDAs on evolution and bio-information levels. In this research, a genome-wide identification of the CDA subfamily in rice (Oryza sativa L.; OsCDAs) was performed, and the phylogeny, gene structure, and biological functions of the identified genes were investigated. The expression profiles of OsCDAs were also retrieved from public microarray databases, and some of OsCDAs expression patterns were further verified by qRT-PCR. The results of this comprehensive analysis suggested that the OsCDAs were highly conserved within species, but their gene structures were relatively divers. OsCDAs may play vital roles during plant development and participate in responses to different biotic and abiotic stresses. The data obtained from this research may provide important information for the functional characterization of CDAs and help to unravel their function in stress tolerance and disease resistance during plant growth and development.