Key message
PpCKX1 localizes to vacuoles and is dominantly expressed in the stem cells. PpCKX1 regulates developmental changes with increased growth of the rhizoid and enhances dehydration and salt ...tolerance.
Cytokinins (CKs) are plant hormones that regulate plant development as well as many physiological processes, such as cell division, leaf senescence, control of shoot/root ratio, and reproductive competence. Cytokinin oxidases/dehydrogenases (CKXs) control CK concentrations by degradation, and thereby influence plant growth and development. In the moss
Physcomitrella patens
, an evolutionarily early divergent plant, we identified six putative
CKX
s that, by phylogenetic analysis, form a monophyletic clade. We also observed that ProPpCKX1:GUS is expressed specifically in the stem cells and surrounding cells and that CKX1 localizes to vacuoles, as indicated by Pro35S:PpCKX1-smGFP. Under normal growth conditions, overexpression of
PpCKX1
caused many phenotypic changes at different developmental stages, and we suspected that increased growth of the rhizoid could affect those changes. In addition, we present evidence that the
PpCKX1
-overexpressor plants show enhanced dehydration and salt stress tolerance. Taken together, we suggest that PpCKX1 plays regulatory roles in development and adaptation to abiotic stresses in this evolutionarily early land plant species.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•AtMYB20-OX showed enhanced while AtMYB20-SRDX showed reduced salt stress tolerance.•PP2Cs were suppressed in AtMYB20-OX and enhanced in AtMYB20-SRDX by NaCl treatment.•AtMYB20 binds to the ABI1 ...promoter region containing a MYB recognition element in vitro.•AtMYB20 binds to the ABI1 and AtPP2CA promoter regions containing an ACGT core element in vitro.•AtMYB20 acts as a negative regulator of PP2Cs to enhance salt tolerance.
We have characterized the function of a plant R2R3-MYB transcription factor, Arabidopsis thaliana MYB20 (AtMYB20). Transgenic plants overexpressing AtMYB20 (AtMYB20-OX) enhanced salt stress tolerance while repression lines (AtMYB20-SRDX) were more vulnerable to NaCl than wild-type plants. Following NaCl treatment, the expressions of ABI1, ABI2 and AtPP2CA, which encode type 2C serine/threonine protein phosphatases (PP2Cs) that act as negative regulators in abscisic acid (ABA) signaling, were suppressed in AtMYB20-OX but induced in AtMYB20-SRDX. The electrophoretic mobility shift assay results revealed that AtMYB20 binds to the promoter regions containing the MYB recognition sequence (TAACTG) and an ACGT core element of ABI1 and AtPP2CA. These findings suggest that AtMYB20 down-regulates the expression of PP2Cs, the negative regulator of ABA signaling, and enhances salt tolerance.
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BFBNIB, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Calmodulins (CaMs) regulate numerous Ca2+-mediated cellular processes in plants by interacting with their respective downstream effectors. Due to the limited number of CaMs, other calcium sensors ...modulate the regulation of Ca2+-mediated cellular processes that are not managed by CaMs. Of 50 CaM-like (CML) proteins identified in Arabidopsis thaliana, we characterized the function of CML10.
Yeast two-hybrid screening revealed phosphomannomutase (PMM) as a putative interaction partner of CML10. In vitro and in vivo interaction assays were performed to analyze the interaction mechanisms of CML10 and PMM. PMM activity and the phenotypes of cml10 knock-down mutants were studied to elucidate the role(s) of the CML10–PMM interaction.
PMM interacted specifically with CML10 in the presence of Ca2+ through its multiple interaction motifs. This interaction promoted the activity of PMM. The phenotypes of cml10 knock-down mutants were more sensitive to stress conditions than wild-type plants, corresponding with the fact that PMM is an enzyme which modulates the biosynthesis of ascorbic acid, an antioxidant.
The results of this research demonstrate that a calcium sensor, CML10, which is an evolutionary variant of CaM, modulates the stress responses in Arabidopsis by regulating ascorbic acid production.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Key message
TCX8 localizes to nucleus and has transcriptional repression activity. TCX8 binds to the promoter region of
LOX2
encoding lipoxygenase, causing JA biosynthesis suppression, and thereby ...delays plant senescence.
Conserved CXC domain-containing proteins are found in most eukaryotes. Eight TCX proteins, which are homologs of animal CXC–Hinge–CXC (CHC) proteins, were identified in
Arabidopsis
, and three of them, TSO1, TCX2/SOL2 and TCX3/SOL1, have been reported to affect cell-cycle control. TCX8, one of the TCX family proteins, was believed to be a TF but its precise function has not been reported. Yeast two-hybrid screening revealed TCP20, a TF that binds to the promoter of
LOX2
encoding lipoxygenase, as a strong candidate for interaction with TCX8. We confirmed that TCX8 directly interacts with TCP20 using in vitro pull-down assay and in vivo BiFC and observed that TCX8, as a TF, localizes to nucleus. Using EMSA and by analyzing phenotypes of
TCX8
-overexpression lines, we demonstrated that TCX8 regulates the expression of
LOX2
by binding to either
cis
-element of
LOX2
promoter to which TCP20 or TCP4 binds, affecting JA biosynthesis, and thereby delaying plant senescence. Our study provides new information about the role of TCX8 in modulating plant senescence through regulating
LOX2
expression.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Drought is the most serious abiotic stress, which significantly reduces crop productivity. The phytohormone ABA plays a pivotal role in regulating stomatal closing upon drought stress. Here, we ...characterized the physiological function of AtBBD1, which has bifunctional nuclease activity, on drought stress. We found that AtBBD1 localized to the nucleus and cytoplasm, and was expressed strongly in trichomes and stomatal guard cells of leaves, based on promoter:GUS constructs. Expression analyses revealed that
and
are induced early and strongly by ABA and drought, and that
is also strongly responsive to JA. We then compared phenotypes of two
-overexpression lines (
-OX), single knockout
, and double knockout
plants under drought conditions. We did not observe any phenotypic difference among them under normal growth conditions, while OX lines had greatly enhanced drought tolerance, lower transpirational water loss, and higher proline content than the WT and KOs. Moreover, by measuring seed germination rate and the stomatal aperture after ABA treatment, we found that
-OX and
plants showed significantly higher and lower ABA-sensitivity, respectively, than the WT. RNA sequencing analysis of
-OX and
plants under PEG-induced drought stress showed that overexpression of
enhances the expression of key regulatory genes in the ABA-mediated drought signaling cascade, particularly by inducing genes related to ABA biosynthesis, downstream transcription factors, and other regulatory proteins, conferring
-OXs with drought tolerance. Taken together, we suggest that AtBBD1 functions as a novel positive regulator of drought responses by enhancing the expression of ABA- and drought stress-responsive genes as well as by increasing proline content.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Key message
The chloroplast-localized protein CSAP is an ABA-responsive factor and positively regulates dark-induced senescence. This phenomenon is controlled by SAUL1 in Arabidopsis.
We report here ...that CSAP (Chloroplast-localized Senescence-Associated Protein, AT5G39520) functions as a positive regulator of senescence and is controlled by SAUL1 (Senescence Associated E3 Ubiquitin Ligase 1) in Arabidopsis.
CSAP
transcript level was gradually increased when senescence was progressed. Under dark conditions, the
csap
mutant showed delayed leaf senescence and reduced chlorophyll breakdown, but overexpression of
CSAP
accelerated leaf senescence and expressions of chlorophyll catabolic genes were up-regulated compared to the wild-type (WT).
NCED3
and
AAO3
, which are involved in ABA biosynthesis, also showed higher expression in the overexpression lines than the WT. It is known that the
CSAP
transcript is increased in the
saul1
mutant that shows precocious senescence. In our experiments, we confirmed that CSAP interacts with SAUL1 by the yeast two-hybrid and pull-down assays. In addition, we found that SAUL1 decreases the stability of CSAP in the presence of ABA. Taken together, we suggest that CSAP accelerates leaf senescence in the dark and this process is controlled by SAUL1.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The hot pepper xyloglucan endo-trans-gluco-sylase/hydrolase (
CaXTH3
) gene that was inducible by a broad spectrum of abiotic stresses in hot pepper has been reported to enhance tolerance to drought ...and high salinity in transgenic
Arabidopsis
. To assess whether
CaXTH3
is a practically useful target gene for improving the stress tolerance of crop plants, we ectopically over-expressed the full-length
CaXTH3
cDNA in tomato (
Solanum lycopersicum
cv. Dotaerang) and found that the
35S:CaXTH3
transgenic tomato plants exhibited a markedly increased tolerance to salt and drought stresses. Transgenic tomato plants exposed to a salt stress of 100 mM NaCl retained the chlorophyll in their leaves and showed normal root elongation. They also remained green and unwithered following exposure to 2 weeks of dehydration. A high proportion of stomatal closures in
35S:CaXTH3
was likely to be conferred by increased cell-wall remodeling activity of CaXTH3 in guard cell, which may reduce transpirational water loss in response to dehydration stress. Despite this increased stress tolerance, the transgenic tomato plants showed no detectable phenotype defects, such as abnormal morphology and growth retardation, under normal growth conditions. These results raise the possibility that
CaXTH3
gene is appropriate for application in genetic engineering strategies aimed at improving abiotic stress tolerance in agriculturally and economically valuable crop plants.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Proline-rich protein (PRP), a cell wall protein of plant, has been studied in many plant species. Yet, none of the PRPs has been functionally elucidated. Here we report a novel flower-specific PRP ...designated OsPRP3 from rice. Expression analysis showed that the OsPRP3 transcript was mainly present in rice flower and accumulated abundantly during the late stage of the flower development. To study the function of OsPRP3, we constructed and transformed a binary vector containing a full clone of OsPRP3 in sense orientation and also an RNAi vector to achieve overexpression and knockout of the gene, respectively. Our overexpression plants showed a significant increase in cold tolerance than the WT plants which is conferred by the accumulation of OsPRP3 protein during cold treatment. Further the microscopic analysis revealed that OsPRP3 enhances the cell wall integrity in the cold tolerant plant and confers cold-tolerance in rice. Microscopic analysis of the RNAi mutant flower revealed that blocking OsPRP3 function caused significant defects in floral organogenesis. Taken together, the results suggested that OsPRP3 is a cell wall protein, playing a crucial role in determining extracellular matrix structure of floral organs.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We investigated the effects of silicon (Si) application on rice plants (Oryza sativa L.) and its responses in the regulation of jasmonic acid (JA) during wounding stress. Endogenous JA was ...significantly higher in wounded rice plants than in non-wounded. In contrast, Si treatment significantly reduced JA synthesis as compared to non-Si applications under wounding stress. mRNA expression of O. sativa genes showed down-regulation of lipoxygenase, allene oxide synthase 1, allene oxide synthase 2, 12-oxophytodienoate reductase 3, and allene oxide cyclase upon Si application and wounding stress as compared to non-Si-treated wounded rice plants. The physical injury-induced-oxidative stress was modulated by Si treatments, which resulted in higher catalase, peroxidase, and polyphenol oxidase activities as compared with non-Si-treated plants under wounding stress. The higher Si accumulation in rice plants also reduced the level of lipid peroxidation, which helped the rice plants to protect it from wounding stress. In conclusion, Si accumulation in rice plants mitigated the adverse effects of wounding through regulation of antioxidants and JA.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In Arabidopsis, the NMD-defective mutants upf1-5 and upf3-1 are characterized by dwarfism, curly leaves and late flowering. These phenotypes are similar to those of mutants showing constitutive ...pathogenesis-related (PR) gene expression, salicylic acid (SA) accumulation and, subsequently, resistance to pathogens. The disease symptoms of upf1-5 and upf3-1 mutants were observed following infection with the virulent pathogen Pst DC3000 with the aim of determining whether the loss of nonsense-mediated mRNA decay (NMD) is involved in disease resistance. These mutant plants showed not only enhanced resistance to Pst DC3000, but also elevated levels of endogenous SA, PR gene transcripts and WRKY transcripts. UPF1 and UPF3 expression was down-regulated in Pst DC3000-infected Arabidopsis plants, but the expression of various NMD target genes was up-regulated. The expression of 10 defense-related genes was elevated in cycloheximide (CHX)-treated plants. The transcriptional ratios of eight of these 10 defense-related genes in CHX-treated to non-treated plants were lower in NMD-defective mutants than in the wild-type plants. These eight defense-related genes are possibly regulated by the NMD mechanism, and it is clear that an alternatively spliced transcript of WRKY62, which contains a premature termination codon, was regulated by this mechanism. Taken together, our results suggest that UPF1 and UPF3, which are key NMD factors, may act as defense-related regulators associated with plant immunity.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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