Over-Expression of Rice CBS Domain Containing Protein, OsCBSX3, Confers Rice Resistance to Magnaporthe oryzae Inoculation

Promotion of apoplastic oxidative burst by artificially selected GhCBSX3A enhances Verticillium dahliae resistance in upland cotton

Verticillium wilt (VW) is a devasting disease affecting various plants, including upland cotton, a crucial fiber crop. Despite its impact, the genetic basis underlying cotton's susceptibility or defense against VW remains unclear. Here, we conducted a genome-wide association study on VW phenotyping in upland cotton and identified a locus on A13 that is significantly associated with VW resistance. We then identified a cystathionine β-synthase domain gene at A13 locus, GhCBSX3A, which was induced by Verticillium dahliae. Functional analysis, including expression silencing in cotton and overexpression in Arabidopsis thaliana, confirmed that GhCBSX3A is a causal gene at the A13 locus, enhancing SAR-RBOHs-mediated apoplastic oxidative burst. We found allelic variation on the TATA-box of GhCBSX3A promoter attenuated its expression in upland cotton, thereby weakening VW resistance. Interestingly, we discovered that altered artificial selection of GhCBSX3A_R (an elite allele for VW) under different VW pressures during domestication and other improved processes allows specific human needs to be met. Our findings underscore the importance of GhCBSX3A in response to VW, and we propose a model for defense-associated genes being selected depending on the pathogen's pressure. The identified locus and gene serve as promising targets for VW resistance enhancement in cotton through genetic engineering.

Curling Leaf 1, Encoding a MYB-Domain Protein, Regulates Leaf Morphology and Affects Plant Yield in Rice

The leaf is the main site of photosynthesis and is an important component in shaping the ideal rice plant architecture. Research on leaf morphology and development will lay the foundation for high-yield rice breeding. In this study, we isolated and identified a novel curling leaf mutant, designated curling leaf 1 (cl1). The cl1 mutant exhibited an inward curling phenotype because of the defective development of sclerenchymatous cells on the abaxial side. Meanwhile, the cl1 mutant showed significant reductions in grain yield and thousand-grain weight due to abnormal leaf development. Through map-based cloning, we identified the CL1 gene, which encodes a MYB transcription factor that is highly expressed in leaves. Subcellular localization studies confirmed its typical nuclear localization. Transcriptome analysis revealed a significant differential expression of the genes involved in photosynthesis, leaf morphology, yield formation, and hormone metabolism in the cl1 mutant. Yeast two-hybrid assays demonstrated that CL1 interacts with alpha-tubulin protein SRS5 and AP2/ERF protein MFS. These findings provide theoretical foundations for further elucidating the mechanisms of CL1 in regulating leaf morphology and offer genetic resources for practical applications in high-yield rice breeding.

The transcribed centromeric gene OsMRPL15 is essential for pollen development in rice

Centromeres consist of highly repetitive sequences that are challenging to map, clone, and sequence. Active genes exist in centromeric regions, but their biological functions are difficult to explore owing to extreme suppression of recombination in these regions. In this study, we used the CRISPR/Cas9 system to knock out the transcribed gene Mitochondrial Ribosomal Protein L15 (OsMRPL15), located in the centromeric region of rice (Oryza sativa) chromosome 8, resulting in gametophyte sterility. Osmrpl15 pollen was completely sterile, with abnormalities appearing at the tricellular stage including the absence of starch granules and disrupted mitochondrial structure. Loss of OsMRPL15 caused abnormal accumulation of mitoribosomal proteins and large subunit rRNA in pollen mitochondria. Moreover, the biosynthesis of several proteins in mitochondria was defective, and expression of mitochondrial genes was upregulated at the mRNA level. Osmrpl15 pollen contained smaller amounts of intermediates related to starch metabolism than wild-type pollen, while biosynthesis of several amino acids was upregulated, possibly to compensate for defective mitochondrial protein biosynthesis and initiate consumption of carbohydrates necessary for starch biosynthesis. These results provide further insight into how defects in mitoribosome development cause gametophyte male sterility.

Genome-wide identification of cystathionine beta synthase genes in wheat and its relationship with anther male sterility under heat stress

Cystathionine beta synthase (CBS) domains containing proteins (CDCPs) plays an important role in plant development through regulation of the thioredoxin system, as well as its ability to respond to biotic and abiotic stress conditions. Despite this, no systematic study has examined the wheat CBS gene family and its relation to high temperature-induced male sterility. In this study, 66 CBS family members were identified in the wheat genome, and their gene or protein sequences were used for subsequent analysis. The TaCBS gene family was found to be unevenly distributed on 21 chromosomes, and they were classified into four subgroups according to their gene structure and phylogeny. The results of collinearity analysis showed that there were 25 shared orthologous genes between wheat, rice and Brachypodium distachyon, and one shared orthologous gene between wheat, millet and barley. The cis-regulatory elements of the TaCBS were related to JA, IAA, MYB, etc. GO and KEGG pathway analysis identified these TaCBS genes to be associated with pollination, reproduction, and signaling and cellular processes, respectively. A heatmap of wheat plants based on transcriptome data showed that TaCBS genes were expressed to a higher extent in spikelets relative to other tissues. In addition, 29 putative tae-miRNAs were identified, targeting 41 TaCBS genes. Moreover, qRT-PCR validation of six TaCBS genes indicated their critical role in anther development, as five of them were expressed at lower levels in heat-stressed male sterile anthers than in Normal anthers. Together with anther phenotypes, paraffin sections, starch potassium iodide staining, and qRT-PCR data, we hypothesized that the TaCBS gene has a very important connection with the heat-stressed sterility process in wheat, and these data provide a basis for further insight into their relationship.

Glutathione S-transferase interactions enhance wheat resistance to powdery mildew but not wheat stripe rust

Wheat stripe rust and powdery mildew are important worldwide diseases of wheat (Triticum aestivum). The wheat cultivar Xingmin318 (XM318) is resistant to both wheat stripe rust and powdery mildew, which are caused by Puccinia striiformis f. sp. tritici (Pst) and Blumeria graminis f. sp. tritici (Bgt), respectively. To explore the difference between wheat defense response against Pst and Bgt, quantitative proteomic analyses of XM318 inoculated with either Pst or Bgt were performed using tandem mass tags technology. A total of 741 proteins were identified as differentially accumulated proteins (DAPs). Bioinformatics analyses indicated that some functional categories, including antioxidant activity and immune system process, exhibited obvious differences between Pst and Bgt infections. Intriguingly, only 42 DAPs responded to both Pst and Bgt infections. Twelve DAPs were randomly selected for reverse transcription quantitative polymerase chain reaction (RT-qPCR) analysis, and the mRNA expression levels of 11 were consistent with their protein expression. Furthermore, gene silencing using the virus-induced gene silencing system indicated that glutathione S-transferase (TaGSTU6) has an important role in resistance to Bgt but not to Pst. TaGSTU6 interacted with the cystathionine beta-synthase (CBS) domain-containing protein (TaCBSX3) in both Pst and Bgt infections. Knockdown of TaCBSX3 expression only reduced wheat resistance to Bgt infection. Overexpression of TaGSTU6 and TaCBSX3 in Arabidopsis (Arabidopsis thaliana) promoted plant resistance to Pseudomonas syringae pv. Tomato DC3000. Our results indicate that TaGSTU6 interaction with TaCBSX3 only confers wheat resistance to Bgt, suggesting that wheat has different response mechanisms to Pst and Bgt stress.

Genome-wide characterization of cys-tathionine-β-synthase domain-containing proteins in sugarcane reveals their role in defense responses under multiple stressors

Cys-tathionine-β-synthase (CBS) domain-containing proteins (CDCPs) are essential for regulating plant responses to various biotic and abiotic stressors. This study describes the systematic identification and characterization of CDCP family genes in Saccharum spontaneum. A total of 95 SsCDCP genes and eight phylogenetic groups were identified that were distributed over 29 chromosomes of the AP85-441 genome. Most (78/95) SsCDCPs underwent fragment duplication events, and 64 gene pairs were located in synteny blocks. Expression profiling of nine ShCDCPs was also carried out in the Saccharum spp. cultivars ROC22 and MT11-611 that are resistant and susceptible to red stripe, respectively, in response to: (i) Infection by the bacterial pathogen Acidovorax avenue subsp. avenae (Aaa); (ii) abiotic stressors (drought and salinity); and (iii) exogenous salicylic acid (SA) treatment. Members of one gene pair (ShCBSD-PB1-5A and ShCBSD-PB1-7A-1) with a fragment duplication event acted as negative regulators in sugarcane under four stresses, as supported by the significantly decreased expression levels of ShCBSD-PB1-5A (23-83%) and ShCBSD-PB1-7A-1 (15-75%) at all-time points, suggesting that they have functional redundancy. Genes in another pair, ShCBS-4C and ShCBS-4D-1, which have a fragment duplication event, play opposing regulatory roles in sugarcane exposed to multiple stresses, particularly Aaa and NaCl treatments. ShCBS-4C expression was significantly decreased by 32-77%, but ShCBS-4D-1 expression was dramatically upregulated by 1.2-6.2-fold in response to Aaa treatment of both cultivars across all-time points. This result suggested that both genes exhibited functional divergence. Meanwhile, the expression of SsCBSDCBS-5A was significantly upregulated in ROC22 by 1.4-4.6-fold in response to the four stressors. These findings provide important clues for further elucidating the function of ShCDCP genes in sugarcane responding to a diverse range of stresses.

All-in-one: a robust fluorescent fusion protein vector toolbox for protein localization and BiFC analyses in plants

Fluorescent tagging protein localization (FTPL) and bimolecular fluorescence complementation (BiFC) are popular tools for in vivo analyses of the subcellular localizations of proteins and protein-protein interactions in plant cells. The efficiency of fluorescent fusion protein (FFP) expression analyses is typically impaired when the FFP genes are co-transformed on separate plasmids compared to when all are cloned and transformed in a single vector. Functional genomics applications using FFPs such as a gene family studies also often require the generation of multiple plasmids. Here, to address these needs, we developed an efficient, modular all-in-one (Aio) FFP (AioFFP) vector toolbox, including a set of fluorescently labelled organelle markers, FTPL and BiFC plasmids and associated binary vectors. This toolbox uses Gibson assembly (GA) and incorporates multiple unique nucleotide sequences (UNSs) to facilitate efficient gene cloning. In brief, this system enables convenient cloning of a target gene into various FFP vectors or the insertion of two or more target genes into the same FFP vector in a single-tube GA reaction. This system also enables integration of organelle marker genes or fluorescently fused target gene expression units into a single transient expression plasmid or binary vector. We validated the AioFFP system by testing genes encoding proteins known to be functional in FTPL and BiFC assays. In addition, we performed a high-throughput assessment of the accurate subcellular localizations of an uncharacterized rice CBSX protein subfamily. This modular UNS-guided GA-mediated AioFFP vector toolkit is cost-effective, easy to use and will promote functional genomics research in plants.

Interaction With Fungi Promotes the Accumulation of Specific Defense Molecules in Orchid Tubers and May Increase the Value of Tubers for Biotechnological and Medicinal Applications: The Case Study of Interaction Between Dactylorhiza sp. and Tulasnella calospora

Terrestrial orchids can form tubers, organs modified to store energy reserves. Tubers are an attractive source of nutrients, and salep, a flour made from dried orchid tubers, is the source of traditional beverages. Tubers also contain valuable secondary metabolites and are used in traditional medicine. The extensive harvest of wild orchids is endangering their populations in nature; however, orchids can be cultivated and tubers mass-produced. This work illustrates the importance of plant-fungus interaction in shaping the content of orchid tubers in vitro. Orchid plants of Dactylorhiza sp. grown in asymbiotic culture were inoculated with a fungal isolate from Tulasnella calospora group and, after 3 months of co-cultivation, tubers were analyzed. The fungus adopted the saprotrophic mode of life, but no visible differences in the morphology and biomass of the tubers were detected compared to the mock-treated plants. To elucidate the mechanisms protecting the tubers against fungal infestation, proteome, metabolome, and lipidome of tubers were analyzed. In total, 1,526, 174, and 108 proteins, metabolites, and lipids were quantified, respectively, providing a detailed snapshot of the molecular process underlying plant-microbe interaction. The observed changes at the molecular level showed that the tubers of inoculated plants accumulated significantly higher amounts of antifungal compounds, including phenolics, alkaloid Calystegine B2, and dihydrophenanthrenes. The promoted antimicrobial effects were validated by observing transient inhibition of Phytophthora cactorum growth. The integration of omics data highlighted the promotion of flavonoid biosynthesis, the increase in the formation of lipid droplets and associated production of oxylipins, and the accumulation of auxin in response to T. calospora. Taken together, these results provide the first insights into the molecular mechanisms of defense priming in orchid tubers and highlight the possible use of fungal interactors in biotechnology for the production of orchid secondary metabolites.

Genome-wide characterization and expression analysis of cystathionine β-synthase genes in plant development and abiotic stresses of cotton (Gossypium spp.)

Cystathionine β-synthase (CBS) domains containing proteins (CDCPs) form a large family and play roles in development via regulation of the thioredoxin system as well as abiotic and biotic stress responses of plant. However, the comprehensive study of CBS genes remained elusive in cotton. Here, we identified 237 CBS genes in 11 plant species and the phylogenetic analysis categorized CBS genes into four groups. Whole-genome or segmental with dispersed duplication events contributed to GhCBS gene family expansion. Moreover, orthologous/paralogous genes among three cotton species (G. hirsutum, G. arboreum, and G. raimondii) were detected from the syntenic map among eight plant species. Strong purifying selection for dicotyledonous and monocotyledonous CBS genes, and cis-elements related to plant growth and development, abiotic and hormonal response were observed. Transcriptomic data and qRT-PCR validation of 12 GhCBS genes indicated their critical role in ovule development as most of the genes showed high enrichment. Further, some of GhCBS (GhCBS5, GhCBS16, GhCBS17, GhCBS24, GhCBS25, GhCBS26, and GhCBS52) genes were regulated under various abiotic and hormonal treatments for different time points and involve in ovule and fiber development which provided key genes for future cotton breeding programs. In addition, transgenic tobacco plants overexpressing GhCBS4 transiently exhibited higher water and chlorophyll content indicating improved tolerance toward drought stress. Overall, this study provides the characterization of GhCBS genes for plant growth, abiotic and hormonal stresses, thereby, intimating their significance in cotton molecular breeding for resistant cultivars.

Proteome changes in pepper (Capsicum annuum L.) leaves induced by the green peach aphid (Myzus persicae Sulzer)

BACKGROUND

Aphid attack induces defense responses in plants activating several signaling cascades that led to the production of toxic, repellent or antinutritive compounds and the consequent reorganization of the plant primary metabolism. Pepper (Capsicum annuum L.) leaf proteomic response against Myzus persicae (Sulzer) has been investigated and analyzed by LC-MS/MS coupled with bioinformatics tools.

RESULTS

Infestation with an initially low density (20 aphids/plant) of aphids restricted to a single leaf taking advantage of clip cages resulted in 6 differentially expressed proteins relative to control leaves (3 proteins at 2 days post-infestation and 3 proteins at 4 days post-infestation). Conversely, when plants were infested with a high density of infestation (200 aphids/plant) 140 proteins resulted differentially expressed relative to control leaves (97 proteins at 2 days post-infestation, 112 proteins at 4 days post-infestation and 105 proteins at 7 days post-infestation). The majority of proteins altered by aphid attack were involved in photosynthesis and photorespiration, oxidative stress, translation, protein folding and degradation and amino acid metabolism. Other proteins identified were involved in lipid, carbohydrate and hormone metabolism, transcription, transport, energy production and cell organization. However proteins directly involved in defense were scarce and were mostly downregulated in response to aphids.

CONCLUSIONS

The unexpectedly very low number of regulated proteins found in the experiment with a low aphid density suggests an active mitigation of plant defensive response by aphids or alternatively an aphid strategy to remain undetected by the plant. Under a high density of aphids, pepper leaf proteome however changed significantly revealing nearly all routes of plant primary metabolism being altered. Photosynthesis was so far the process with the highest number of proteins being regulated by the presence of aphids. In general, at short times of infestation (2 days) most of the altered proteins were upregulated. However, at longer times of infestation (7 days) the protein downregulation prevailed. Proteins involved in plant defense and in hormone signaling were scarce and mostly downregulated.

Functional Analysis of Wheat NAC Transcription Factor, TaNAC069, in Regulating Resistance of Wheat to Leaf Rust Fungus

NAC transcription factors are one of the largest transcription factor families having functions in a variety of stress responses. Few NACs have been reported for interactions between wheat and the wheat rust fungus Puccinia triticina (Pt). In this study, based on analysis of RNA-seq data from wheat line TcLr19 inoculated by Pt, the NAC transcription factor TaNAC069 was cloned from wheat, and its transcriptional activity and homologous dimer formation were verified. Quantitative real-time PCR analysis showed that the expression of TaNAC069 was induced by Pt and associated signaling molecules. To further characterize the function of the TaNAC069 gene in wheat resistance to Pt, virus-induced gene silencing (VIGS) was utilized, and it revealed that Pt resistance in TaNAC069-silenced plants was significantly reduced. Potential interaction targets of TaNAC069 from wheat and Pt were screened and identified by yeast two-hybrid technology. Eukaryotic elongation factor eEF1A, CBSX3 protein, and cold acclimation protein WCOR410c were screened by yeast one-hybrid technology. The results indicate that the TaNAC069 gene plays a positive regulatory role in wheat resistance to Pt, laying a good foundation to analyze the molecular mechanisms of TaNAC069 and its functional role in wheat resistance to Pt.

Proteomic analysis upon peach fruit infection with Monilinia fructicola and M. laxa identify responses contributing to brown rot resistance

Brown rot, caused by Monilinia spp., is a major peach disease worldwide. In this study, the response of peach cultivars Royal Glory (RG) and Rich Lady (RL) to infection by Monilinia fructicola or Monilinia laxa, was characterized. Phenotypic data, after artificial inoculations, revealed that ‘RL’ was relatively susceptible whereas ‘RG’ was moderately resistant to Monilinia spp. Comparative proteomic analysis identified mesocarp proteins of the 2 cultivars whose accumulation were altered by the 2 Monilinia species. Functional analysis indicated that pathogen-affected proteins in ‘RG’ were mainly involved in energy and metabolism, while, differentially accumulated proteins by the pathogen presence in ‘RL’ were involved in disease/defense and metabolism. A higher number of proteins was differentiated in ‘RG’ fruit compared to ‘RL’. Upon Monilinia spp. infection, various proteins were-down accumulated in ‘RL’ fruit. Protein identification by mass spectrometric analysis revealed that several defense-related proteins including thaumatin, formate dehydrogenase, S-formylglutathione hydrolase, CBS domain-containing protein, HSP70, and glutathione S-transferase were up-accumulated in ‘RG’ fruit following inoculation. The expression profile of selected defense-related genes, such as major latex allergen, 1-aminocyclopropane-1-carboxylate deaminase and UDP-glycoltransferase was assessed by RT-PCR. This is the first study deciphering differential regulations of peach fruit proteome upon Monilinia infection elucidating resistance responses.

DEGENERATED PANICLE AND PARTIAL STERILITY 1 (DPS1) encodes a cystathionine β-synthase domain containing protein required for anther cuticle and panicle development in rice

Degeneration of apical spikelets and reduced panicle fertility are common reasons for low seed-setting rate in rice (Oryza sativa). However, little is known about the underlying molecular mechanisms. Here, we report a novel degenerated panicle and partial sterility 1 (dps1) mutant that showed panicle apical degeneration and reduced fertility in middle spikelets. dps1 plants were characterized by small whitish anthers with altered cuticle morphology and absence of pollen grains. Amounts of cuticular wax and cutin were significantly reduced in dps1 anthers. Panicles of dps1 plants showed an accumulation of reactive oxygen species (ROS), lower antioxidant activity, and increased programmed cell death. Map-based cloning revealed that DPS1 encodes a mitochondrial-localized protein containing a cystathionine β-synthase domain that showed the highest expression in panicles and anthers. DPS1 physically interacted with mitochondrial thioredoxin proteins Trx1 and Trx20, and it participated in ROS scavenging. Global gene expression analysis in dps1 revealed that biological processes related to fatty acid metabolism and ROS homeostasis were significantly affected, and the expression of key genes involved in wax and cutin biosynthesis were downregulated. These results suggest that DPS1 plays a vital role in regulating ROS homeostasis, anther cuticle formation, and panicle development in rice.

BjuWRR1, a CC-NB-LRR gene identified in Brassica juncea, confers resistance to white rust caused by Albugo candida

BjuWRR1, a CNL-type R gene, was identified from an east European gene pool line of Brassica juncea and validated for conferring resistance to white rust by genetic transformation. White rust caused by the oomycete pathogen Albugo candida is a significant disease of crucifer crops including Brassica juncea (mustard), a major oilseed crop of the Indian subcontinent. Earlier, a resistance-conferring locus named AcB1-A5.1 was mapped in an east European gene pool line of B. juncea-Donskaja-IV. This line was tested along with some other lines of B. juncea (AABB), B. rapa (AA) and B. nigra (BB) for resistance to six isolates of A. candida collected from different mustard growing regions of India. Donskaja-IV was found to be completely resistant to all the tested isolates. Sequencing of a BAC spanning the locus AcB1-A5.1 showed the presence of a single CC-NB-LRR protein encoding R gene. The genomic sequence of the putative R gene with its native promoter and terminator was used for the genetic transformation of a susceptible Indian gene pool line Varuna and was found to confer complete resistance to all the isolates. This is the first white rust resistance-conferring gene described from Brassica species and has been named BjuWRR1. Allelic variants of the gene in B. juncea germplasm and orthologues in the Brassicaceae genomes were studied to understand the evolutionary dynamics of the BjuWRR1 gene.

Label-free proteomic analysis of silkworm midgut infected by Bombyx mori nuclear polyhedrosis virus

Bombyx mori nuclear polyhedrosis virus (BmNPV) is the most damaging virus for the production of silkworm cocoons. Antivirus research continues to be an important aspect of the silkworm industry. Two-dimensional electrophoresis and mass spectrometry have been applied for analyzing the midgut proteome of BmNPV-infected silkworms. In recent years, the isobaric tags for relative and absolute quantitation (iTRAQ) method has frequently been used when studying interaction between BmNPV and Bombyx mori, and useful information has been obtained. In this study, midgut proteins of BmNPV-infected silkworms were extracted from silkworm variety NIL·LVR with anti-BmNPV activity at 48 h, and proteome analysis was carried out using the label-free method. 2196 proteins were identified. Among them, there were 85 differentially expressed proteins, 45 upregulated proteins (immune-activated proteins), 28 downregulated proteins, and six proteins were specific for the BmNPV group and another six specific for control group. Many of the immune-activated proteins have been reported to have innate immune functions, and the downregulated proteins are involved in apoptosis or abnormal cell viability. In conclusion, this study provides evidence for host defense against BmNPV infection by both innate immunity and apoptosis, revealing the potential function of the midgut after oral infection of BmNPV in Bombyx mori. SIGNIFICANCE: Bombyx mori nuclear polyhedrosis virus (BmNPV) has a great impact on the sericulture industry. However, the mechanism of resistance to BmNPV has not been fully elucidated. The silkworm midgut is not only the major organ for food digestion and nutrient absorption but also an immune organ serving as the first line of defense against microbial invasion and proliferation. Here we combined label-free quantitative proteomic, bioinformatics, quantitative real-time PCR and SDS-PAGE analyses and found that BmNPV invasion causes complex protein alterations in the larval midgut of NIL·LVR with anti-BmNPV activity. The results showed that many upregulated differentially expressed proteins have been reported to have innate immune functions and the downregulation proteins are involved in apoptosis or abnormal cell viability. These findings provide evidence for host defense against BmNPV infection by both innate immunity and apoptosis, and reveals the potential function of the midgut after infection of BmNPV in Bombyx mori.

ZmMADS69 functions as a flowering activator through the ZmRap2.7-ZCN8 regulatory module and contributes to maize flowering time adaptation

Flowering time is a major determinant of the local adaptation of plants. Although numerous loci affecting flowering time have been mapped in maize, their underlying molecular mechanisms and roles in adaptation remain largely unknown. Here, we report the identification and characterization of MADS-box transcription factor ZmMADS69 that functions as a flowering activator through the ZmRap2.7-ZCN8 regulatory module and contributes to adaptation. We show that ZmMADS69 underlies a quantitative trait locus controlling the difference in flowering time between maize and its wild ancestor, teosinte. Maize ZmMADS69 allele is expressed at a higher level at floral transition and confers earlier flowering than the teosinte allele under long days and short days. Overexpression of ZmMADS69 causes early flowering, while a transposon insertion mutant of ZmMADS69 exhibits delayed flowering. ZmMADS69 shows pleiotropic effects for multiple traits of agronomic importance. ZmMADS69 functions upstream of the flowering repressor ZmRap2.7 to downregulate its expression, thereby relieving the repression of the florigen gene ZCN8 and causing early flowering. Population genetic analyses showed that ZmMADS69 was a target of selection and may have played an important role as maize spread from the tropics to temperate zones. Our findings provide important insights into the regulation and adaptation of flowering time.

ERECT LEAF1 suppresses jasmonic acid response in rice by decreasing OsWRKY4 stability

ERECT LEAF 1 (ELF1), which was identified as a component of brassinosteroid signaling in rice, is involved in brassinosteroid-mediated suppression of jasmonic acid response. Here, by conducting yeast two-hybrid assay and in vitro ubiquitination experiments, we demonstrate that ELF1 interacts with the OsWRKY4 transcription factor, a positive regulator of defense responses to rice sheath blight. ELF1 decreased the stability of OsWRKY4, whereas exogenous jasmonic acid treatment suppressed this effect of ELF1, resulting in OsWRKY4 accumulation in rice plants. In wild-type rice, OsWRKY4 expression was up-regulated by jasmonic acid treatment but down-regulated by brassinosteroid treatment, suggesting that jasmonic acid-induced OsWRKY4 accumulation was caused by a combination of increased production and suppressed degradation. The expression levels of the OsWRKY4 target genes, PR1b and PR5, seemed to be correlated with the OsWRKY4 level. These results suggest that ELF1 indirectly controls the expression of PR1b and PR5 genes by regulating the OsWRKY4 protein level, and support a hypothesis that brassinosteroid and jasmonic acid cooperate to maintain the balance between growth and defense responses. We conclude that ELF1 participates in the antagonistic interaction between these two phytohormones by suppressing the jasmonic acid response through the down-regulation of OsWRKY4 protein level in rice.

Characterization of Transcription Factor Gene OsDRAP1 Conferring Drought Tolerance in Rice

HIGHLIGHTS Overexpressing and RNA interfering OsDRAP1 transgenic rice plants exhibited significantly improved and reduced drought tolerance, but accompanied with negative effects on development and yield. The dehydration responsive element binding (DREBs) genes are important transcription factors which play a crucial role in plant abiotic stress tolerances. In this study, we functionally characterized a DREB2-like gene, OsDRAP1 conferring drought tolerance (DT) in rice. OsDRAP1, containing many cis-elements in its promoter region, was expressed in all organs (mainly expressed in vascular tissues) of rice, and induced by a variety of environmental stresses and plant hormones. Overexpressing OsDRAP1 transgenic plants exhibited significantly improved DT; while OsDRAP1 RNA interfering plants exhibited significantly reduced DT which also accompanied with significant negative effects on development and yield. Overexpression of OsDRAP1 has a positive impact on maintaining water balance, redox homeostasis and vascular development in transgenic rice plants under drought stress. OsDRAP1 interacted with many genes/proteins and could activate many downstream DT related genes, including important transcription factors such as OsCBSX3 to response drought stress, indicating the OsDRAP1-mediated pathways for DT involve complex genes networks. All these results provide a basis for further complete understanding of the OsDRAP1 mediated gene networks and their related phenotypic effects.

OsCBSCBSPB4 is a Two Cystathionine-β-Synthase Domain-containing Protein from Rice that Functions in Abiotic Stress Tolerance

Cystathionine β-synthase (CBS) domains have been identified in a wide range of proteins of unrelated functions such as, metabolic enzymes, kinases and channels, and usually occur as tandem re-peats, often in combination with other domains. In plants, CBS Domain-Containing Proteins (CDCPs) form a multi-gene family and only a few are so far been reported to have a role in development via regu-lation of thioredoxin system as well as in abiotic and biotic stress response. However, the function of majority of CDCPs still remains to be elucidated in plants. Here, we report the cloning, characterization and functional validation of a CBS domain containing protein, OsCBSCBSPB4 from rice, which pos-sesses two CBS domains and one PB1 domain. We show that OsCBSCBSPB4 encodes a nucleo-cytoplasmic protein whose expression is induced in response to various abiotic stress conditions in salt-sensitive IR64 and salt-tolerant Pokkali rice cultivars. Further, heterologous expression of OsCBSCB-SPB4 in E. coli and tobacco confers marked tolerance against various abiotic stresses. Transgenic tobac-co seedlings over-expressing OsCBSCBSPB4 were found to exhibit better growth in terms of delayed leaf senescence, profuse root growth and increased biomass in contrast to the wild-type seedlings when subjected to salinity, dehydration, oxidative and extreme temperature treatments. Yeast-two hybrid stud-ies revealed that OsCBSCBSPB4 interacts with various proteins. Of these, some are known to be in-volved in abiotic stress tolerance. Our results suggest that OsCBSCBSPB4 is involved in abiotic stress response and is a potential candidate for raising multiple abiotic stress tolerant plants.