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Zhou CM, Li JX, Zhang TQ, Xu ZG, Ma ML, Zhang P, Wang JW. The structure of B-ARR reveals the molecular basis of transcriptional activation by cytokinin. Proc Natl Acad Sci U S A 2024; 121:e2319335121. [PMID: 38198526 PMCID: PMC10801921 DOI: 10.1073/pnas.2319335121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Accepted: 12/11/2023] [Indexed: 01/12/2024] Open
Abstract
The phytohormone cytokinin has various roles in plant development, including meristem maintenance, vascular differentiation, leaf senescence, and regeneration. Prior investigations have revealed that cytokinin acts via a phosphorelay similar to the two-component system by which bacteria sense and respond to external stimuli. The eventual targets of this phosphorelay are type-B ARABIDOPSIS RESPONSE REGULATORS (B-ARRs), containing the conserved N-terminal receiver domain (RD), middle DNA binding domain (DBD), and C-terminal transactivation domain. While it has been established for two decades that the phosphoryl transfer from a specific histidyl residue in ARABIDOPSIS HIS PHOSPHOTRANSFER PROTEINS (AHPs) to an aspartyl residue in the RD of B-ARRs results in a rapid transcriptional response to cytokinin, the underlying molecular basis remains unclear. In this work, we determine the crystal structures of the RD-DBD of ARR1 (ARR1RD-DBD) as well as the ARR1DBD-DNA complex from Arabidopsis. Analyses of the ARR1DBD-DNA complex have revealed the structural basis for sequence-specific recognition of the GAT trinucleotide by ARR1. In particular, comparing the ARR1RD-DBD and ARR1DBD-DNA structures reveals that unphosphorylated ARR1RD-DBD exists in a closed conformation with extensive contacts between the RD and DBD. In vitro and vivo functional assays have further suggested that phosphorylation of the RD weakens its interaction with DBD, subsequently permits the DNA binding capacity of DBD, and promotes the transcriptional activity of ARR1. Our findings thus provide mechanistic insights into phosphorelay activation of gene transcription in response to cytokinin.
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Affiliation(s)
- Chuan-Miao Zhou
- National Key Laboratory of Plant Molecular Genetics, Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai200032, China
| | - Jian-Xu Li
- National Key Laboratory of Plant Molecular Genetics, Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai200032, China
- Shanghai Key Laboratory of Plant Functional Genomics and Resources, Shanghai Chenshan Botanical Garden, Shanghai Chenshan Plant Science Research Center, Chinese Academy of Sciences, Shanghai201602, China
| | - Tian-Qi Zhang
- National Key Laboratory of Plant Molecular Genetics, Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai200032, China
| | - Zhou-Geng Xu
- National Key Laboratory of Plant Molecular Genetics, Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai200032, China
| | - Miao-Lian Ma
- National Key Laboratory of Plant Molecular Genetics, Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai200032, China
| | - Peng Zhang
- National Key Laboratory of Plant Molecular Genetics, Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai200032, China
- Key Laboratory of Plant Carbon Capture, Chinese Academy of Sciences, Shanghai200032, China
| | - Jia-Wei Wang
- National Key Laboratory of Plant Molecular Genetics, Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai200032, China
- Key Laboratory of Plant Carbon Capture, Chinese Academy of Sciences, Shanghai200032, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai201210, China
- New Cornerstone Science Laboratory, Shanghai200032, China
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Li L, Zhang X, Ding F, Hou J, Wang J, Luo R, Mao W, Li X, Zhu H, Yang L, Li Y, Hu J. Genome-wide identification of the melon (Cucumis melo L.) response regulator gene family and functional analysis of CmRR6 and CmPRR3 in response to cold stress. JOURNAL OF PLANT PHYSIOLOGY 2024; 292:154160. [PMID: 38147808 DOI: 10.1016/j.jplph.2023.154160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 12/03/2023] [Accepted: 12/07/2023] [Indexed: 12/28/2023]
Abstract
The response regulator (RR) gene family play crucial roles in cytokinin signal transduction, plant development, and resistance to abiotic stress. However, there are no reports on the identification and functional characterization of RR genes in melon. In this study, a total of 18 CmRRs were identified and classified into type A, type B, and clock PRRs, based on phylogenetic analysis. Most of the CmRRs displayed tissue-specific expression patterns, and some were induced by cold stress according to two RNA-seq datasets. The expression patterns of CmRR2/6/11/15 and CmPRR2/3 under cold treatment were confirmed by qRT-PCR. Subcellular localization assays indicated that CmRR6 and CmPRR3 were primarily localized in the nucleus and chloroplast. Furthermore, when either CmRR6 or CmPRR3 were silenced using tobacco ringspot virus (TRSV), the cold tolerance of the virus-induced gene silencing (VIGS) melon plants were significantly enhanced, as evidenced by measurements of chlorophyll fluorescence, ion leakage, reactive oxygen, proline, and malondialdehyde levels. Additionally, the expression levels of CmCBF1, CmCBF2, and CmCBF3 were significantly increased in CmRR6-silenced and CmPRR3-silenced plants under cold treatment. Our findings suggest that CmRRs contribute to cold stress responses and provide new insights for further pursuing the molecular mechanisms underlying CmRRs-mediated cold tolerance in melon.
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Affiliation(s)
- Lili Li
- College of Horticulture, Henan Agricultural University, Zhengzhou, 450046, China
| | - Xiuyue Zhang
- College of Horticulture, Henan Agricultural University, Zhengzhou, 450046, China
| | - Fei Ding
- College of Horticulture, Henan Agricultural University, Zhengzhou, 450046, China
| | - Juan Hou
- College of Horticulture, Henan Agricultural University, Zhengzhou, 450046, China; Research Center of Cucurbit Germplasm Enhancement and Utilization of Henan Province, Zhengzhou, 450046, China
| | - Jiyu Wang
- College of Horticulture, Henan Agricultural University, Zhengzhou, 450046, China
| | - Renren Luo
- College of Horticulture, Henan Agricultural University, Zhengzhou, 450046, China
| | - Wenwen Mao
- College of Horticulture, Henan Agricultural University, Zhengzhou, 450046, China; Research Center of Cucurbit Germplasm Enhancement and Utilization of Henan Province, Zhengzhou, 450046, China
| | - Xiang Li
- College of Horticulture, Henan Agricultural University, Zhengzhou, 450046, China; International Joint Laboratory of Henan Horticultural Crop Biology, Pingan Avenue 218, Zhengdong New District, Zhengzhou, 450046, China
| | - Huayu Zhu
- College of Horticulture, Henan Agricultural University, Zhengzhou, 450046, China; International Joint Laboratory of Henan Horticultural Crop Biology, Pingan Avenue 218, Zhengdong New District, Zhengzhou, 450046, China
| | - Luming Yang
- College of Horticulture, Henan Agricultural University, Zhengzhou, 450046, China; International Joint Laboratory of Henan Horticultural Crop Biology, Pingan Avenue 218, Zhengdong New District, Zhengzhou, 450046, China
| | - Ying Li
- College of Horticulture, Henan Agricultural University, Zhengzhou, 450046, China.
| | - Jianbin Hu
- College of Horticulture, Henan Agricultural University, Zhengzhou, 450046, China; Research Center of Cucurbit Germplasm Enhancement and Utilization of Henan Province, Zhengzhou, 450046, China.
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Li L, Sun X, Yu W, Gui M, Qiu Y, Tang M, Tian H, Liang G. Comparative transcriptome analysis of high- and low-embryogenic Hevea brasiliensis genotypes reveals involvement of phytohormones in somatic embryogenesis. BMC PLANT BIOLOGY 2023; 23:489. [PMID: 37828441 PMCID: PMC10571474 DOI: 10.1186/s12870-023-04432-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 08/31/2023] [Indexed: 10/14/2023]
Abstract
BACKGROUND Rubber plant (Hevea brasiliensis) is one of the major sources of latex. Somatic embryogenesis (SE) is a promising alterative to its propagation by grafting and seed. Phytohormones have been shown to influence SE in different plant species. However, limited knowledge is available on the role of phytohormones in SE in Hevea. The anther cultures of two Hevea genotypes (Yunyan 73477-YT and Reken 628-RT) with contrasting SE rate were established and four stages i.e., anthers (h), anther induced callus (y), callus differentiation state (f), and somatic embryos (p) were studied. UPLC-ESI-MS/MS and transcriptome analyses were used to study phytohormone accumulation and related expression changes in biosynthesis and signaling genes. RESULTS YT showed higher callus induction rate than RT. Of the two genotypes, only YT exhibited successful SE. Auxins, cytokinins (CKs), abscisic acid (ABA), jasmonic acid (JA), salicylic acid (SA), gibberellins (GAs), and ethylene (ETH) were detected in the two genotypes. Indole-3-acetic acid (IAA), CKs, ABA, and ETH had notable differences in the studied stages of the two genotypes. The differentially expressed genes identified in treatment comparisons were majorly enriched in MAPK and phytohormone signaling, biosynthesis of secondary metabolites, and metabolic pathways. The expression changes in IAA, CK, ABA, and ETH biosynthesis and signaling genes confirmed the differential accumulation of respective phytohormones in the two genotypes. CONCLUSION These results suggest potential roles of phytohormones in SE in Hevea.
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Affiliation(s)
- Ling Li
- The Center of Rubber Research, Yunnan Institute of Tropical Crops, Xishuangbanna, China
| | - Xiaolong Sun
- The Center of Rubber Research, Yunnan Institute of Tropical Crops, Xishuangbanna, China
| | - Wencai Yu
- The Center of Rubber Research, Yunnan Institute of Tropical Crops, Xishuangbanna, China
| | - Mingchun Gui
- The Center of Rubber Research, Yunnan Institute of Tropical Crops, Xishuangbanna, China
| | - Yanfen Qiu
- The Center of Rubber Research, Yunnan Institute of Tropical Crops, Xishuangbanna, China
| | - Min Tang
- The Center of Rubber Research, Yunnan Institute of Tropical Crops, Xishuangbanna, China
| | - Hai Tian
- The Center of Rubber Research, Yunnan Institute of Tropical Crops, Xishuangbanna, China
| | - Guoping Liang
- The Center of Rubber Research, Yunnan Institute of Tropical Crops, Xishuangbanna, China.
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Liao LY, He ZQ, Zhang L. Cloning and Functional Analysis of the VfRR17 Gene from tung tree ( Vernicia fordii). PLANTS (BASEL, SWITZERLAND) 2023; 12:2474. [PMID: 37447035 DOI: 10.3390/plants12132474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 06/24/2023] [Accepted: 06/26/2023] [Indexed: 07/15/2023]
Abstract
Tung tree (Vernicia fordii) is one of the four major woody oilseed species in China. However, its fruit yield is severely hampered by the low number of female flowers and the imbalanced male-to-female flower ratio, which is a problem that restricts the development of the oilseed industry. Previous research has demonstrated that the exogenous application of cytokinins can significantly augment the number of female flowers, although the underlying regulatory mechanism remains elusive. To elucidate the involvement of VfRR17, a member of the A-type ARRs family, in the exogenous cytokinin regulation of flower sexual differentiation in tung tree, this study conducted a comprehensive bioinformatic analysis of the physicochemical properties, structural characteristics, and evolutionary relationships of the protein encoded by VfRR17. Additionally, gene function analysis was performed using subcellular localization, qRT-PCR, and genetic transformation techniques. The findings revealed that the VfRR17 gene's coding region spanned 471 bp, encoding an unstable protein of 156 amino acids with a relative molecular mass of 17.4 kDa. Phylogenetic analysis demonstrated a higher similarity between VfRR17 of the tung tree and the RR17 gene of Jatropha curcas, Ricinus communis, Hevea brasiliensis, and other species within the Euphorbiaceae family compared to other species, with the greatest similarity of 86% observed with the RR17 gene of Jatropha curcas. The qRT-PCR analysis indicated that VfRR17 exhibited high expression levels during the early stage of tung tree inflorescence buds following 6-BA treatment, peaking at 24 h and displaying a 3.47-fold increase compared to that at 0 h. In female and male flowers of the tung tree, the expression in female flowers during the 1 DBF period was significantly higher than in male flowers, exhibiting a difference of approximately 47.91-fold. Furthermore, notable differential expression was observed in the root, leaf, and petiole segments of the tung tree under low-temperature stress at the 12-h time point. In transgenic Arabidopsis, the VfRR17 lines and wild-type lines exhibited significantly different flowering times under an exogenous 6-BA treatment at a concentration of 2 mg/L, with the VfRR17 lines experiencing an 11-day delay compared to the wild-type lines. Additionally, the number of fruit pods in VfRR17 transgenic Arabidopsis lines was significantly reduced by 28 compared to the wild-type lines at a 6-BA concentration of 3 mg/L. These findings suggest that VfRR17 likely plays a critical role in regulating flower development in response to exogenous 6-BA, providing valuable insights into the mechanisms underlying exogenous 6-BA-mediated regulation of female flower development in the tung tree.
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Affiliation(s)
- Li-Yu Liao
- Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees, Ministry of Education, Central South University of Forestry and Technology, Changsha 410004, China
- Key Lab of Non-Wood Forest Products of State Forestry and Grassland Administration, Central South University of Forestry and Technology, Changsha 410004, China
| | - Zhang-Qi He
- Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees, Ministry of Education, Central South University of Forestry and Technology, Changsha 410004, China
- Key Lab of Non-Wood Forest Products of State Forestry and Grassland Administration, Central South University of Forestry and Technology, Changsha 410004, China
| | - Lin Zhang
- Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees, Ministry of Education, Central South University of Forestry and Technology, Changsha 410004, China
- Key Lab of Non-Wood Forest Products of State Forestry and Grassland Administration, Central South University of Forestry and Technology, Changsha 410004, China
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Lv Z, Yu L, Zhan H, Li J, Wang C, Huang L, Wang S. Shoot differentiation from Dendrocalamus brandisii callus and the related physiological roles of sugar and hormones during shoot differentiation. TREE PHYSIOLOGY 2023:tpad039. [PMID: 36988419 DOI: 10.1093/treephys/tpad039] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 02/20/2023] [Indexed: 06/19/2023]
Abstract
Only a few calli regeneration systems of bamboos were successfully established, which limited the research on physiological mechanism of callus differentiation. In this study, we successfully established the callus differentiation systems of Dendrocalamus brandisii via seeds. The results showed that the best medium for callus induction of D. brandisii seeds was basal MS media amended with 5.0 mg L-1 2,4-D and 0.5 mg L-1 KT, and the optimal medium for shoot differentiation was the basal MS media supplemented with 4.0 mg L-1 BA and 0.5 mg L-1 NAA. Callus tissues had apparent polarity in cell arrangement, and developed their own meristematic cell layers. α-amylase, STP and SUSY played a dominant role in carbohydrates degradation in callus during shoot differentiation. PPP and TCA pathways up-regulated in the shoot-differentiated calli. The dynamics of BA and KT contents in calli was consistent with their concentrations applied in medium. IAA synthesis and the related signal transduction were down-regulated, while the endogenous CTKs contents were up-regulated by the exogenous CTKs application in shoot-differentiated calli, and their related synthesis, transport and signal transduction pathways were also up-regulated. The downregulated signal transduction pathways of IAA and ABA revealed that they did not play the key role in shoot differentiation of bamboos. GAs also played a role in shoot differentiation based on the down-regulation of DELLA and the up-regulation of PIF4 genes. The overexpression of DbSNRK2 and DbFIF4 genes further confirmed the negative role of ABA and the positive role of GAs in shoot differentiation.
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Affiliation(s)
- Zhuo Lv
- Faculty of Life Sciences, Southwest Forestry University, Kunming, China
- Bamboo Research Institute, Nanjing Forestry University, Nanjing, China
| | - Lixia Yu
- Faculty of Life Sciences, Southwest Forestry University, Kunming, China
- Faculty of Bamboo and Rattan, Southwest Forestry University, Kunming, China
| | - Hui Zhan
- Faculty of Life Sciences, Southwest Forestry University, Kunming, China
- Faculty of Bamboo and Rattan, Southwest Forestry University, Kunming, China
| | - Juan Li
- Faculty of Life Sciences, Southwest Forestry University, Kunming, China
- Faculty of Bamboo and Rattan, Southwest Forestry University, Kunming, China
| | - Changming Wang
- Faculty of Life Sciences, Southwest Forestry University, Kunming, China
- Faculty of Bamboo and Rattan, Southwest Forestry University, Kunming, China
| | - Ling Huang
- Faculty of Life Sciences, Southwest Forestry University, Kunming, China
| | - Shuguang Wang
- Faculty of Life Sciences, Southwest Forestry University, Kunming, China
- Faculty of Bamboo and Rattan, Southwest Forestry University, Kunming, China
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Cho LH, Yoon J, Tun W, Baek G, Peng X, Hong WJ, Mori IC, Hojo Y, Matsuura T, Kim SR, Kim ST, Kwon SW, Jung KH, Jeon JS, An G. Cytokinin increases vegetative growth period by suppressing florigen expression in rice and maize. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 110:1619-1635. [PMID: 35388561 DOI: 10.1111/tpj.15760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/17/2022] [Accepted: 03/28/2022] [Indexed: 05/12/2023]
Abstract
Increasing the vegetative growth period of crops can increase biomass and grain yield. In rice (Oryza sativa), the concentration of trans -zeatin, an active cytokinin, was high in the leaves during vegetative growth and decreased rapidly upon induction of florigen expression, suggesting that this hormone is involved in the regulation of the vegetative phase. To elucidate whether exogenous cytokinin application influences the length of the vegetative phase, we applied 6-benzylaminopurine (BAP) to rice plants at various developmental stages. Our treatment delayed flowering time by 8-9 days when compared with mock-treated rice plants, but only at the transition stage when the flowering signals were produced. Our observations also showed that flowering in the paddy field is delayed by thidiazuron, a stable chemical that mimics the effects of cytokinin. The transcript levels of florigen genes Heading date 3a (Hd3a) and Rice Flowering locus T1 (RFT1) were significantly reduced by the treatment, but the expression of Early heading date 1 (Ehd1), a gene found directly upstream of the florigen genes, was not altered. In maize (Zea mays), similarly, BAP treatment increased the vegetative phage by inhibiting the expression of ZCN8, an ortholog of Hd3a. We showed that cytokinin treatment induced the expression of two type-A response regulators (OsRR1 and OsRR2) which interacted with Ehd1, a type-B response regulator. We also observed that cytokinin did not affect flowering time in ehd1 knockout mutants. Our study indicates that cytokinin application increases the duration of the vegetative phase by delaying the expression of florigen genes in rice and maize by inhibiting Ehd1.
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Affiliation(s)
- Lae-Hyeon Cho
- Department of Plant Bioscience, Life and Industry Convergence Research Institute, Pusan National University, Miryang, 50463, Republic of Korea
- Crop Biotech Institute and Graduate School of Biotechnology, Kyung Hee University, Yongin, 17104, South Korea
| | - Jinmi Yoon
- Department of Plant Bioscience, Life and Industry Convergence Research Institute, Pusan National University, Miryang, 50463, Republic of Korea
- Crop Biotech Institute and Graduate School of Biotechnology, Kyung Hee University, Yongin, 17104, South Korea
| | - Win Tun
- Crop Biotech Institute and Graduate School of Biotechnology, Kyung Hee University, Yongin, 17104, South Korea
| | - Gibeom Baek
- Department of Plant Bioscience, Life and Industry Convergence Research Institute, Pusan National University, Miryang, 50463, Republic of Korea
| | - Xin Peng
- Crop Biotech Institute and Graduate School of Biotechnology, Kyung Hee University, Yongin, 17104, South Korea
- Institute of Genomics and Bioinformatics, South China Agricultural University, Guangzhou, 510642, China
| | - Woo-Jong Hong
- Crop Biotech Institute and Graduate School of Biotechnology, Kyung Hee University, Yongin, 17104, South Korea
| | - Izumi C Mori
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, 710-0046, Japan
| | - Yuko Hojo
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, 710-0046, Japan
| | - Takakazu Matsuura
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, 710-0046, Japan
| | - Sung-Ryul Kim
- Novel Gene Resources Laboratory, Strategic Innovation Platform, International Rice Research Institute (IRRI), DAPO Box 7777, Metro Manila, Philippines
| | - Sun-Tae Kim
- Department of Plant Bioscience, Life and Industry Convergence Research Institute, Pusan National University, Miryang, 50463, Republic of Korea
| | - Soon-Wook Kwon
- Department of Plant Bioscience, Life and Industry Convergence Research Institute, Pusan National University, Miryang, 50463, Republic of Korea
| | - Ki-Hong Jung
- Crop Biotech Institute and Graduate School of Biotechnology, Kyung Hee University, Yongin, 17104, South Korea
| | - Jong-Seong Jeon
- Crop Biotech Institute and Graduate School of Biotechnology, Kyung Hee University, Yongin, 17104, South Korea
| | - Gynheung An
- Crop Biotech Institute and Graduate School of Biotechnology, Kyung Hee University, Yongin, 17104, South Korea
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Shih HW, Alas GCM, Paredez AR. A cell-cycle-dependent GARP-like transcriptional repressor regulates the initiation of differentiation in Giardia lamblia. Proc Natl Acad Sci U S A 2022; 119:e2204402119. [PMID: 35613049 PMCID: PMC9295799 DOI: 10.1073/pnas.2204402119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 04/21/2022] [Indexed: 11/18/2022] Open
Abstract
Transcriptional regulation of differentiation is critical for parasitic pathogens to adapt to environmental changes and regulate transmission. In response to encystation stimuli, Giardia lamblia shifts the distribution of the cell cycle toward G2 and induces the expression of cyst wall proteins (CWPs) within 2 to 4 h, indicating that key regulatory steps occur within the first 4 h of encystation. However, the role of transcription factors (TFs) in encystation has primarily been investigated at later time points. How TFs initiate encystation and link it to the cell cycle remains enigmatic. Here, we systematically screened six putative early up-regulated TFs for nuclear localization, established their dynamic expression profiles, and determined their functional role in regulating encystation. We found a critical repressor, Golden2, ARR-B, Psr-1–like protein 1 (GARP)–like protein 4 (GLP4), that increases rapidly after 30 min of encystation stimuli and down-regulates encystation-specific markers, including CWPs and enzymes in the cyst N-acetylgalactosamine pathway. Depletion of GLP4 increases cyst production. Importantly, we observe that G2+M cells exhibit higher levels of CWP1, resulting from the activation of myeloblastosis domain protein 2 (MYB2), a TF previously linked to encystation in Giardia. GLP4 up-regulation occurs in G1+S cells, suggesting a role in repressing MYB2 and encystation-specific genes in the G1+S phase of the cell cycle. Furthermore, we demonstrate that depletion of GLP4 up-regulates MYB2 and promotes encystation while overexpression of GLP4 down-regulates MYB2 and represses encystation. Together, these results suggest that Giardia employs a dose-dependent transcriptional response that involves the cell-cycle–regulated repressor GLP4 to orchestrate MYB2 and entry into the encystation pathway.
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Affiliation(s)
- Han-Wei Shih
- Department of Biology, University of Washington, Seattle, WA 98195
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Yamoune A, Cuyacot AR, Zdarska M, Hejatko J. Hormonal orchestration of root apical meristem formation and maintenance in Arabidopsis. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:6768-6788. [PMID: 34343283 DOI: 10.1093/jxb/erab360] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 08/02/2021] [Indexed: 06/13/2023]
Abstract
Plant hormones are key regulators of a number of developmental and adaptive responses in plants, integrating the control of intrinsic developmental regulatory circuits with environmental inputs. Here we provide an overview of the molecular mechanisms underlying hormonal regulation of root development. We focus on key events during both embryonic and post-embryonic development, including specification of the hypophysis as a future organizer of the root apical meristem (RAM), hypophysis asymmetric division, specification of the quiescent centre (QC) and the stem cell niche (SCN), RAM maturation and maintenance of QC/SCN activity, and RAM size. We address both well-established and newly proposed concepts, highlight potential ambiguities in recent terminology and classification criteria of longitudinal root zonation, and point to contrasting results and alternative scenarios for recent models. In the concluding remarks, we summarize the common principles of hormonal control during root development and the mechanisms potentially explaining often antagonistic outputs of hormone action, and propose possible future research directions on hormones in the root.
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Affiliation(s)
- Amel Yamoune
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology and National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic
| | - Abigail Rubiato Cuyacot
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology and National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic
| | - Marketa Zdarska
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology and National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic
| | - Jan Hejatko
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology and National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic
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Li Y, Fan Y, Jiao Y, Wu J, Zhang Z, Yu X, Ma Y. Transcriptome profiling of yellow leafy head development during the heading stage in Chinese cabbage (Brassica rapa subsp. pekinensis). PHYSIOLOGIA PLANTARUM 2019; 165:800-813. [PMID: 29900559 DOI: 10.1111/ppl.12784] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Revised: 05/31/2018] [Accepted: 06/10/2018] [Indexed: 05/16/2023]
Abstract
The yellow leafy head of Brassica rapa is known to be tasty and nutritional. Therefore, the heading stage of leaf development is critical to realize high yield and economic benefits. A widely planted commercial cultivar of B. rapa ('Qiubao', deep yellow leafy head) was used to conduct transcriptome analysis. The results showed that the yellowing of the inner leaf was likely induced by the predominant β-carotene biosynthesis pathway due to the upregulated gene geranylgeranyl diphosphate and phytoene synthase, and the downregulated gene CrtL-e, NCED4 and DWARF-27. Some genes related to chlorophyll synthesis were also found to be downregulated, such as nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase and protochlorophyllide reductase A. Transcript profiling also revealed strong changes in expression levels of hormonal genes related to auxin, cytokinin, ethylene, abscisic acid, gibberellin and brassinosteroids, suggesting the crucial role that hormones play in heading stage. Examination of carbohydrate and sucrose metabolism pathways revealed that sucrose biosynthesis is probably regulated by 6-phosphofructokinase and sucrose synthase 1 (SUS1/SuSy1) branch, instead of the sucrose-phosphate synthase branch. Several cold-response genes were induced in the late-heading stage, but the results suggest that the common C-repeat binding factor responsive pathway may not be involved in cold adaption. We also identified a series of upregulated transcription factors-AP2/ERF, MYB, bHLH, NAC and WRKY were found to be predominant. The transcripts analysis provides a preliminary genetic resource to unravel key genes and molecular mechanisms responsible for leafy head development in B. rapa, therefore, improving leafy head quality and yield through genetic means in future.
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Affiliation(s)
- Yuefei Li
- Liaoning Engineering Research Center of Meat Processing and Quality Safety Control, Department of Food Science and Engineering, Jinzhou Medical University, Jinzhou 121000, China
| | - Yong Fan
- Liaoning Research Institute of Cash Crops, Liaoyang 111000, China
| | - Yang Jiao
- Liaoning Engineering Research Center of Meat Processing and Quality Safety Control, Department of Food Science and Engineering, Jinzhou Medical University, Jinzhou 121000, China
| | - Jie Wu
- Liaoning Engineering Research Center of Meat Processing and Quality Safety Control, Department of Food Science and Engineering, Jinzhou Medical University, Jinzhou 121000, China
| | - Zhen Zhang
- Liaoning Engineering Research Center of Meat Processing and Quality Safety Control, Department of Food Science and Engineering, Jinzhou Medical University, Jinzhou 121000, China
| | - Xiaolei Yu
- Liaoning Engineering Research Center of Meat Processing and Quality Safety Control, Department of Food Science and Engineering, Jinzhou Medical University, Jinzhou 121000, China
| | - Ying Ma
- Liaoning Engineering Research Center of Meat Processing and Quality Safety Control, Department of Food Science and Engineering, Jinzhou Medical University, Jinzhou 121000, China
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10
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Cho LH, Yoon J, Pasriga R, An G. Homodimerization of Ehd1 Is Required to Induce Flowering in Rice. PLANT PHYSIOLOGY 2016; 170:2159-71. [PMID: 26864016 PMCID: PMC4825144 DOI: 10.1104/pp.15.01723] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 02/02/2016] [Indexed: 05/20/2023]
Abstract
In plants, flowering time is elaborately controlled by various environment factors. Ultimately, florigens such as FLOWERING LOCUS T (FT) or FT-like molecules induce flowering. In rice (Oryza sativa), Early heading date 1 (Ehd1) is a major inducer of florigen gene expression. Although Ehd1 is highly homologous to the type-B response regulator (RR) family in the cytokinin signaling pathway, its precise molecular mechanism is not well understood. In this study, we showed that the C-terminal portion of the protein containing the GARP DNA-binding (G) domain can promote flowering when overexpressed. We also observed that the N-terminal portion of Ehd1, carrying the receiver (R) domain, delays flowering by inhibiting endogenous Ehd1 activity. Ehd1 protein forms a homomer via a 16-amino acid region in the inter domain between R and G. From the site-directed mutagenesis analyses, we demonstrated that phosphorylation of the Asp-63 residue within the R domain induces the homomerization of Ehd1, which is crucial for Ehd1 activity. A type-A RR, OsRR1, physically interacts with Ehd1 to form a heterodimer. In addition, OsRR1-overexpressing plants show a late-flowering phenotype. Based on these observations, we conclude that OsRR1 inhibits Ehd1 activity by binding to form an inactive complex.
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Affiliation(s)
- Lae-Hyeon Cho
- Crop Biotech Institute, Kyung Hee University, Yongin 446-701, Korea (L.-H.C., J.Y., R.P., G.A.);Department of Life Science, Pohang University of Science and Technology, Pohang 790-784, Korea (L.-H.C., J.Y.); andGraduate School of Biotechnology, Kyung Hee University, Yongin 446-701, Korea (R.P., G.A.)
| | - Jinmi Yoon
- Crop Biotech Institute, Kyung Hee University, Yongin 446-701, Korea (L.-H.C., J.Y., R.P., G.A.);Department of Life Science, Pohang University of Science and Technology, Pohang 790-784, Korea (L.-H.C., J.Y.); andGraduate School of Biotechnology, Kyung Hee University, Yongin 446-701, Korea (R.P., G.A.)
| | - Richa Pasriga
- Crop Biotech Institute, Kyung Hee University, Yongin 446-701, Korea (L.-H.C., J.Y., R.P., G.A.);Department of Life Science, Pohang University of Science and Technology, Pohang 790-784, Korea (L.-H.C., J.Y.); andGraduate School of Biotechnology, Kyung Hee University, Yongin 446-701, Korea (R.P., G.A.)
| | - Gynheung An
- Crop Biotech Institute, Kyung Hee University, Yongin 446-701, Korea (L.-H.C., J.Y., R.P., G.A.);Department of Life Science, Pohang University of Science and Technology, Pohang 790-784, Korea (L.-H.C., J.Y.); andGraduate School of Biotechnology, Kyung Hee University, Yongin 446-701, Korea (R.P., G.A.)
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11
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Pacifici E, Polverari L, Sabatini S. Plant hormone cross-talk: the pivot of root growth. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:1113-21. [PMID: 25628331 DOI: 10.1093/jxb/eru534] [Citation(s) in RCA: 121] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Root indeterminate growth and its outstanding ability to produce new tissues continuously make this organ a highly dynamic structure able to respond promptly to external environmental stimuli. Developmental processes therefore need to be finely tuned, and hormonal cross-talk plays a pivotal role in the regulation of root growth. In contrast to what happens in animals, plant development is a post-embryonic process. A pool of stem cells, placed in a niche at the apex of the meristem, is a source of self-renewing cells that provides cells for tissue formation. During the first days post-germination, the meristem reaches its final size as a result of a balance between cell division and cell differentiation. A complex network of interactions between hormonal pathways co-ordinates such developmental inputs. In recent years, by means of molecular and computational approaches, many efforts have been made aiming to define the molecular components of these networks. In this review, we focus our attention on the molecular mechanisms at the basis of hormone cross-talk during root meristem size determination.
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Affiliation(s)
- Elena Pacifici
- Department of Biology and Biotechnology, Laboratory of Functional Genomics and Proteomics of Model Systems, University of Rome Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Laura Polverari
- Department of Biology and Biotechnology, Laboratory of Functional Genomics and Proteomics of Model Systems, University of Rome Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Sabrina Sabatini
- Department of Biology and Biotechnology, Laboratory of Functional Genomics and Proteomics of Model Systems, University of Rome Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy
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12
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Hacham Y, Koussevitzky S, Kirma M, Amir R. Glutathione application affects the transcript profile of genes in Arabidopsis seedling. JOURNAL OF PLANT PHYSIOLOGY 2014; 171:1444-51. [PMID: 25077999 DOI: 10.1016/j.jplph.2014.06.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Revised: 06/24/2014] [Accepted: 06/24/2014] [Indexed: 05/21/2023]
Abstract
Glutathione (GSH), a tripeptide thiol compound has multiple functions in plants. Recent works suggested that GSH plays a regulatory role in signaling in plants as part of their adaptation to stress. To better understand the role of GSH as a regulatory molecule, 14 days old Arabidopsis thaliana seedlings were treated with 5mM of GSH for 4h. Changes in gene expression patterns were studied by cDNA microarray analysis. The expression of 453 genes was significantly changed compared to the untreated control, of which 261 genes were up-regulated and 192 genes were down-regulated. Genes from several groups were affected, including those of sulfur metabolism, degradation and synthesis of macromolecules and transcription factors. Up-regulation of genes involved in responses to biotic stresses, or in jasmonate or salicylic acid synthesis and their signaling, suggests that GSH triggers genes that help protect the plants during stresses. In addition, GSH down regulated genes involved in plant growth and development, like those involved in cell wall synthesis and its extension, and genes associated with auxin and cytokinins response, which are related to growth and development of the plants. The results suggest that GSH might have a role in response to biotic stress by initiating defense responses and modifying plants' growth and development in an effort to tune their sessile lifestyle of plants to environmental constraints.
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Affiliation(s)
- Yael Hacham
- Laboratory of Plant Science, Migal Galilee Research Institute, P.O. Box 831, Kiryat Shmona 12100, Israel
| | - Shai Koussevitzky
- Laboratory of Plant Science, Migal Galilee Research Institute, P.O. Box 831, Kiryat Shmona 12100, Israel
| | - Menny Kirma
- Department of Plant Science, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Rachel Amir
- Laboratory of Plant Science, Migal Galilee Research Institute, P.O. Box 831, Kiryat Shmona 12100, Israel; Tel Hai College, Upper Galilee, Israel.
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13
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Immanen J, Nieminen K, Duchens Silva H, Rodríguez Rojas F, Meisel LA, Silva H, Albert VA, Hvidsten TR, Helariutta Y. Characterization of cytokinin signaling and homeostasis gene families in two hardwood tree species: Populus trichocarpa and Prunus persica. BMC Genomics 2013; 14:885. [PMID: 24341635 PMCID: PMC3866579 DOI: 10.1186/1471-2164-14-885] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 11/27/2013] [Indexed: 01/01/2023] Open
Abstract
Background Through the diversity of cytokinin regulated processes, this phytohormone has a profound impact on plant growth and development. Cytokinin signaling is involved in the control of apical and lateral meristem activity, branching pattern of the shoot, and leaf senescence. These processes influence several traits, including the stem diameter, shoot architecture, and perennial life cycle, which define the development of woody plants. To facilitate research about the role of cytokinin in regulation of woody plant development, we have identified genes associated with cytokinin signaling and homeostasis pathways from two hardwood tree species. Results Taking advantage of the sequenced black cottonwood (Populus trichocarpa) and peach (Prunus persica) genomes, we have compiled a comprehensive list of genes involved in these pathways. We identified genes belonging to the six families of cytokinin oxidases (CKXs), isopentenyl transferases (IPTs), LONELY GUY genes (LOGs), two-component receptors, histidine containing phosphotransmitters (HPts), and response regulators (RRs). All together 85 Populus and 45 Prunus genes were identified, and compared to their Arabidopsis orthologs through phylogenetic analyses. Conclusions In general, when compared to Arabidopsis, differences in gene family structure were often seen in only one of the two tree species. However, one class of genes associated with cytokinin signal transduction, the CKI1-like family of two-component histidine kinases, was larger in both Populus and Prunus than in Arabidopsis.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Ykä Helariutta
- Institute of Biotechnology and Department of Biosciences, University of Helsinki, FI-00014 Helsinki, Finland.
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14
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Kang NY, Cho C, Kim J. Inducible expression of Arabidopsis response regulator 22 (ARR22), a type-C ARR, in transgenic Arabidopsis enhances drought and freezing tolerance. PLoS One 2013; 8:e79248. [PMID: 24244460 PMCID: PMC3828410 DOI: 10.1371/journal.pone.0079248] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 09/20/2013] [Indexed: 12/14/2022] Open
Abstract
The Arabidopsis two-component signaling system, which is comprised of sensor histidine kinases, histidine phosphotransfer proteins, and response regulators, mediates cytokinin response as well as various other plant responses including abiotic stress responses. Arabidopsis response regulators (ARRs) are classified into type-A, -B, and -C. Although the roles of type-A and -B ARRs are well established in Arabidopsis plant signaling, roles of type-C ARRs, ARR22 and ARR24, remain elusive. ARR22, a preferentially cytosolic protein, interacts with certain Arabidopsis histidine phosphotransfer proteins (AHPs) and displays phosphatase activity on AHP5. ARR22 is induced by cold and dehydration. Here, we show that inducible overexpression of ARR22 in Arabidopsis enhanced dehydration, drought, and cold tolerance in a dexamethasone-dependent manner, whereas mutation of the putative phospho-accepting Asp to Asn in ARR22 (ARR22D74N) abolished these tolerance phenotypes. Overexpression of ARR22 decreased electrolyte leakage in dehydration-, drought-, or cold-stressed transgenic Arabidopsis plants compared with that of ARR22D74N or compared with wild-type plants. Transpiration rates and stomatal apertures were not affected by ARR22 overexpression. No significant difference in both dehydration and freezing tolerance was observed between wild-type and arr22 mutants with or without cytokinin preincubation, consistent with the lack of phenotypes of arr22 mutants in their vegetative development. Meta-profile analyses of the microarray data on ARR22-responsive genes indicate that ARR22 modulates expression of a variety of abiotic stress-responsive genes, which might contribute to increasing drought and freezing tolerance. Taken together, these results suggest that ARR22 plays a positive role in the stress tolerance response in part via enhancing cell membrane integrity and that phospho-histidine phosphatase activity of ARR22 may be required for this function.
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Affiliation(s)
- Na Young Kang
- Department of Bioenergy Science and Technology and Kumho Life Science Laboratory, Chonnam National University, Buk-Gu, Gwangju, Korea
| | - Chuloh Cho
- Department of Bioenergy Science and Technology and Kumho Life Science Laboratory, Chonnam National University, Buk-Gu, Gwangju, Korea
| | - Jungmook Kim
- Department of Bioenergy Science and Technology and Kumho Life Science Laboratory, Chonnam National University, Buk-Gu, Gwangju, Korea
- * E-mail:
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15
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Del Bianco M, Giustini L, Sabatini S. Spatiotemporal changes in the role of cytokinin during root development. THE NEW PHYTOLOGIST 2013; 199:324-338. [PMID: 23692218 DOI: 10.1111/nph.12338] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Accepted: 04/12/2013] [Indexed: 05/07/2023]
Abstract
The root is a dynamic system whose structure is regulated by a complex network of interactions between hormones. The primary root meristem is specified in the embryo. After germination, the primary root meristem grows and then reaches a final size that will be maintained during the life of the plant. Subsequently, secondary structures such as lateral roots and root nodules form via the re-specification of differentiated cells. Cytokinin plays key roles in the regulation of root development. Down-regulation of the cytokinin response is required for the specification of a new stem cell niche, during both embryo and lateral root development. In the root meristem, cytokinin signalling regulates the longitudinal zonation of the meristem by controlling cell differentiation. Moreover, cytokinin regulates radial patterning of root vasculature by promoting protophloem cell identity and by spatially inhibiting protoxylem formation. In this review, an effort is made to describe the known details of the role of cytokinin during root development, taking into account also the interactions between cytokinin and other hormones. Attention is given on the dynamicity of cytokinin signalling output during different developmental events. Indeed, there is much evidence that the effects of cytokinin change as organs grow, underlining the importance of the spatiotemporal specificity of cytokinin signalling.
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Affiliation(s)
- Marta Del Bianco
- Laboratory of Functional Genomics and Proteomics of Model Systems, Dipartimento di Biologia e Biotecnologie, Università di Roma, Sapienza - via dei Sardi, 70-00185, Rome, Italy
| | - Leonardo Giustini
- Laboratory of Functional Genomics and Proteomics of Model Systems, Dipartimento di Biologia e Biotecnologie, Università di Roma, Sapienza - via dei Sardi, 70-00185, Rome, Italy
| | - Sabrina Sabatini
- Laboratory of Functional Genomics and Proteomics of Model Systems, Dipartimento di Biologia e Biotecnologie, Università di Roma, Sapienza - via dei Sardi, 70-00185, Rome, Italy
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16
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Veerabagu M, Elgass K, Kirchler T, Huppenberger P, Harter K, Chaban C, Mira-Rodado V. The Arabidopsis B-type response regulator 18 homomerizes and positively regulates cytokinin responses. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 72:721-31. [PMID: 22775331 DOI: 10.1111/j.1365-313x.2012.05101.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In higher plants, the two-component system (TCS) is a signaling mechanism based on a His-to-Asp phosphorelay. The Arabidopsis TCS involves three different types of proteins, namely the histidine kinases (AHKs), the histidine phosphotransfer proteins (AHPs) and the response regulators (ARRs). The ARRs comprise three different families, namely A, B and C types, according to their protein structure. While some members of the B-type family of ARRs have been studied extensively and reported to act as DNA-binding transcriptional regulators, very limited information is available for other B-type ARRs such as ARR18. In this study, we characterize in detail the molecular and functional properties of ARR18. ARR18 acts as a transcriptional regulator in plant cells and forms homodimers in planta as shown by FRET-FLIM studies. As demonstrated by mutational analysis, the aspartate at position 70 (D70) in the receiver domain of ARR18 acts as crucial phosphorylation site. The modification of D70 affects the response regulator's ability to homodimerize and to activate its target genes. Furthermore, physiological investigations of Arabidopsis lines ectopically expressing ARR18 introduce ARR18 as a new member within the cytokinin-regulated response pathway regulating root elongation.
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Affiliation(s)
- Manikandan Veerabagu
- Center for Plant Molecular Biology-ZMBP, Department of Plant Physiology, University of Tübingen, Auf der Morgenstelle 1, 72076 Tübingen, Germany
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17
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Kang NY, Cho C, Kim NY, Kim J. Cytokinin receptor-dependent and receptor-independent pathways in the dehydration response of Arabidopsis thaliana. JOURNAL OF PLANT PHYSIOLOGY 2012; 169:1382-91. [PMID: 22704545 DOI: 10.1016/j.jplph.2012.05.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Revised: 05/18/2012] [Accepted: 05/18/2012] [Indexed: 05/05/2023]
Abstract
Cytokinin signaling in Arabidopsis thaliana utilizes a multi-step two-component signaling (TCS) system comprised of sensor histidine kinases (AHKs), histidine phosphotransfer proteins (AHPs), and response regulators (ARRs). Recent studies have suggested that the cytokinin TCS system is involved in a variety of other signaling and metabolic pathways. To further explore a potential function of the cytokinin TCS in the Arabidopsis dehydration stress response, we investigated the expression of all type-A ARR genes and a type-C ARR, ARR22, in both wild type and ahk single, double, and triple mutants in response to dehydration compared to cytokinin as well as dehydration tolerance of ahk mutants. We found that drought significantly induced the expression of a subset of ARR genes, ARR5, ARR7, ARR15, and ARR22. The results of expression analyses in ahk single, double, and triple mutants demonstrated that the cytokinin receptors AHK2 and AHK3 are redundantly involved in dehydration-inducible expression of ARR7, but not that of ARR5, ARR15, or ARR22. Dehydration tolerance assays showed that ahk2 and ahk3 single mutants exhibited enhanced dehydration tolerance compared with that of wild-type plants and ahk4 mutants, and that ahk2 ahk3 double mutants exhibited stronger drought tolerance than that of ahk3 ahk4, which exhibited more enhanced drought tolerance than that of wild-type plants and ahk single mutants. Taken together, these results demonstrate that while the cytokinin receptors AHK2 and AHK3 are critically involved in the dehydration tolerance response, both cytokinin receptor-dependent pathway and receptor-independent pathway occur in the dehydration response regulating ARR gene expression. In addition, preincubating ahk2, ahk3, ahk4, and the wild-type plants with cytokinin induced enhanced dehydration stress tolerance in these plants, demonstrating that cytokinins are involved in regulating plant response to dehydration stress.
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Affiliation(s)
- Na Young Kang
- Department of Bioenergy Science and Technology and Kumho Life Science Laboratory, Chonnam National University, Buk-Gu, Gwangju 500-757, Republic of Korea
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18
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Shao X, Yang R, Wang J, Fang Q, Yao B, Wang Y, Sun Y, Li X. The altered responses of a new mutant long life span 1 to cytokinin in Arabidopsis thaliana. J Genet Genomics 2012; 39:139-48. [PMID: 22464473 DOI: 10.1016/j.jgg.2011.10.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Revised: 10/25/2011] [Accepted: 10/26/2011] [Indexed: 10/14/2022]
Abstract
Cytokinins are a class of essential plant hormones regulating plant growth and development. Although the two-component phosphorelay pathway of cytokinin has been well characterized, the intact cytokinin responses regulation picture still needs to be fully depicted. Here we report a new mutant, long life span 1 (lls1), which displays dwarf stature, curled leaves, numerous axillary branches and nearly 5-month life span. Exogenous cytokinin could not recover the phenotypes of the mutant. Moreover, mutation in lls1 suppressed the cytokinin-responsive phenotypes, including root and hypocotyl growth inhibition, anthocyanin accumulation, metaxylem promotion in primary root development. The induction of cytokinin-responsive genes, ARR5, AHP5, and CKX3, was also suppressed in lls1. According to quantitative RT-PCR (qRT-PCR) and microarray results, the basal expression of positive factors AHP5, ARR1, and ARR10 were down-regulated, while the negative factors ARR4 and ARR5 were up-regulated. Our results suggested that LLS1 gene might be involved in the regulation of cytokinin signaling. It was mapped to chromosome 4 where no other cytokinin relevant gene has been reported.
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Affiliation(s)
- Xinghua Shao
- School of Life Science, East China Normal University, Shanghai 200062, China
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