1
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Jia T, Wang H, Cui S, Li Z, Shen Y, Li H, Xiao G. Cotton BLH1 and KNOX6 antagonistically modulate fiber elongation via regulation of linolenic acid biosynthesis. PLANT COMMUNICATIONS 2024; 5:100887. [PMID: 38532644 PMCID: PMC11287173 DOI: 10.1016/j.xplc.2024.100887] [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: 10/06/2023] [Revised: 01/19/2024] [Accepted: 03/23/2024] [Indexed: 03/28/2024]
Abstract
BEL1-LIKE HOMEODOMAIN (BLH) proteins are known to function in various plant developmental processes. However, the role of BLHs in regulating plant cell elongation is still unknown. Here, we identify a BLH gene, GhBLH1, that positively regulates fiber cell elongation. Combined transcriptomic and biochemical analyses reveal that GhBLH1 enhances linolenic acid accumulation to promote cotton fiber cell elongation by activating the transcription of GhFAD7A-1 via binding of the POX domain of GhBLH1 to the TGGA cis-element in the GhFAD7A-1 promoter. Knockout of GhFAD7A-1 in cotton significantly reduces fiber length, whereas overexpression of GhFAD7A-1 results in longer fibers. The K2 domain of GhKNOX6 directly interacts with the POX domain of GhBLH1 to form a functional heterodimer, which interferes with the transcriptional activation of GhFAD7A-1 via the POX domain of GhBLH1. Overexpression of GhKNOX6 leads to a significant reduction in cotton fiber length, whereas knockout of GhKNOX6 results in longer cotton fibers. An examination of the hybrid progeny of GhBLH1 and GhKNOX6 transgenic cotton lines provides evidence that GhKNOX6 negatively regulates GhBLH1-mediated cotton fiber elongation. Our results show that the interplay between GhBLH1 and GhKNOX6 modulates regulation of linolenic acid synthesis and thus contributes to plant cell elongation.
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Affiliation(s)
- Tingting Jia
- College of Life Sciences, Shihezi University, Shihezi 832003, China
| | - Huiqin Wang
- College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China
| | - Shiyan Cui
- Zhengzhou Research Base, State Key Laboratory of Cotton Biology, School of Agricultural Sciences, Zhengzhou University, Zhengzhou 450001, China
| | - Zihan Li
- Geosystems Research Institute, Mississippi State University, Starkville, MS 39762, USA
| | - Yongcui Shen
- College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China
| | - Hongbin Li
- College of Life Sciences, Shihezi University, Shihezi 832003, China.
| | - Guanghui Xiao
- College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China.
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2
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Lu Z, Zhang J, Wang H, Zhang K, Gu Z, Xu Y, Zhang J, Wang M, Han L, Xiang F, Zhou C. Rewiring of a KNOXI regulatory network mediated by UFO underlies the compound leaf development in Medicago truncatula. Nat Commun 2024; 15:2988. [PMID: 38582884 PMCID: PMC10998843 DOI: 10.1038/s41467-024-47362-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 03/28/2024] [Indexed: 04/08/2024] Open
Abstract
Class I KNOTTED-like homeobox (KNOXI) genes are parts of the regulatory network that control the evolutionary diversification of leaf morphology. Their specific spatiotemporal expression patterns in developing leaves correlate with the degrees of leaf complexity between simple-leafed and compound-leafed species. However, KNOXI genes are not involved in compound leaf formation in several legume species. Here, we identify a pathway for dual repression of MtKNOXI function in Medicago truncatula. PINNATE-LIKE PENTAFOLIATA1 (PINNA1) represses the expression of MtKNOXI, while PINNA1 interacts with MtKNOXI and sequesters it to the cytoplasm. Further investigations reveal that UNUSUAL FLORAL ORGANS (MtUFO) is the direct target of MtKNOXI, and mediates the transition from trifoliate to pinnate-like pentafoliate leaves. These data suggest a new layer of regulation for morphological diversity in compound-leafed species, in which the conserved regulators of floral development, MtUFO, and leaf development, MtKNOXI, are involved in variation of pinnate-like compound leaves in M. truncatula.
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Affiliation(s)
- Zhichao Lu
- The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Juanjuan Zhang
- The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Hongfeng Wang
- The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
- Shandong Peanut Research Institute, Qingdao, 266199, China
| | - Ke Zhang
- The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Zhiqun Gu
- The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Yiteng Xu
- The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Jing Zhang
- The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Min Wang
- The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Lu Han
- The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Fengning Xiang
- The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Chuanen Zhou
- The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China.
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3
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Hertig C, Rutten T, Melzer M, Schippers JHM, Thiel J. Dissection of Developmental Programs and Regulatory Modules Directing Endosperm Transfer Cell and Aleurone Identity in the Syncytial Endosperm of Barley. PLANTS (BASEL, SWITZERLAND) 2023; 12:1594. [PMID: 37111818 PMCID: PMC10142620 DOI: 10.3390/plants12081594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 03/10/2023] [Accepted: 04/04/2023] [Indexed: 06/19/2023]
Abstract
Endosperm development in barley starts with the formation of a multinucleate syncytium, followed by cellularization in the ventral part of the syncytium generating endosperm transfer cells (ETCs) as first differentiating subdomain, whereas aleurone (AL) cells will originate from the periphery of the enclosing syncytium. Positional signaling in the syncytial stage determines cell identity in the cereal endosperm. Here, we performed a morphological analysis and employed laser capture microdissection (LCM)-based RNA-seq of the ETC region and the peripheral syncytium at the onset of cellularization to dissect developmental and regulatory programs directing cell specification in the early endosperm. Transcriptome data revealed domain-specific characteristics and identified two-component signaling (TCS) and hormone activities (auxin, ABA, ethylene) with associated transcription factors (TFs) as the main regulatory links for ETC specification. On the contrary, differential hormone signaling (canonical auxin, gibberellins, cytokinin) and interacting TFs control the duration of the syncytial phase and timing of cellularization of AL initials. Domain-specific expression of candidate genes was validated by in situ hybridization and putative protein-protein interactions were confirmed by split-YFP assays. This is the first transcriptome analysis dissecting syncytial subdomains of cereal seeds and provides an essential framework for initial endosperm differentiation in barley, which is likely also valuable for comparative studies with other cereal crops.
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Affiliation(s)
- Christian Hertig
- Department of Physiology and Cell Biology, Leibniz Institute for Plant Genetics and Crop Plant Research (IPK), D-06466 Seeland, Germany
| | - Twan Rutten
- Department of Physiology and Cell Biology, Leibniz Institute for Plant Genetics and Crop Plant Research (IPK), D-06466 Seeland, Germany
| | - Michael Melzer
- Department of Physiology and Cell Biology, Leibniz Institute for Plant Genetics and Crop Plant Research (IPK), D-06466 Seeland, Germany
| | - Jos H. M. Schippers
- Department of Molecular Genetics, Leibniz Institute for Plant Genetics and Crop Plant Research (IPK), D-06466 Seeland, Germany
| | - Johannes Thiel
- Department of Molecular Genetics, Leibniz Institute for Plant Genetics and Crop Plant Research (IPK), D-06466 Seeland, Germany
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4
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Fang SC, Chen JC, Chang PY, Lin HY. Co-option of the SHOOT MERISTEMLESS network regulates protocorm-like body development in Phalaenopsis aphrodite. PLANT PHYSIOLOGY 2022; 190:127-145. [PMID: 35258627 PMCID: PMC9434259 DOI: 10.1093/plphys/kiac100] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 01/08/2022] [Indexed: 06/02/2023]
Abstract
The protocorm is a structure that is formed upon germination of an orchid seed. It lacks cotyledons and is ovoid in shape. The protocorm-like body (PLB), on the other hand, is a protocorm-like organ induced from somatic tissues. PLBs have been widely used for orchid micropropagation. Because of its unique structure and its application in the orchid industry, PLB development has drawn considerable interest from orchid and developmental biologists. Our previous genome-wide comparative transcriptome study demonstrated that protocorms and PLBs share similar molecular signatures and suggested that SHOOT MERISTEMLESS (STM)-dependent organogenesis is important for PLB development. Here, we show that overexpression of Phalaenopsis aphrodite STM (PaSTM) greatly enhances PLB regeneration from vegetative tissue-based explants of Phalaenopsis orchids, confirming its regulatory role in PLB development. Expression of PaSTM restored shoot meristem function of the Arabidopsis (Arabidopsis thaliana) stm-2 mutant. Moreover, we identified class S11 MYB transcription factors (TFs) as targets downstream of PaSTM. A cis-acting element, TTGACT, identified in the promoters of S11 MYB TFs was found to be important for PaSTM binding and activation. Overexpression of PaSTM or its downstream targets, PaMYB13, PaMYB14, and PaMYB17, enhanced de novo shoot regeneration in Arabidopsis, indicating the active role of the PaSTM-S11 PaMYB module in organogenesis. In summary, our data demonstrate that PaSTM is important for PLB development. The STM-S11 MYB regulatory module is evolutionarily conserved and may regulate shoot or shoot-related organ development in plants.
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Affiliation(s)
| | - Jhun-Chen Chen
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 741, Taiwan
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Pou-Yi Chang
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 741, Taiwan
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Hsiang-Yin Lin
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 741, Taiwan
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
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5
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Zhao Y, Zhang Y, Zhang W, Shi Y, Jiang C, Song X, Tuskan GA, Zeng W, Zhang J, Lu M. The PagKNAT2/6b-PagBOP1/2a Regulatory Module Controls Leaf Morphogenesis in Populus. Int J Mol Sci 2022; 23:ijms23105581. [PMID: 35628391 PMCID: PMC9145908 DOI: 10.3390/ijms23105581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 05/12/2022] [Accepted: 05/15/2022] [Indexed: 12/04/2022] Open
Abstract
Leaf morphogenesis requires precise regulation of gene expression to achieve organ separation and flat-leaf form. The poplar KNOTTED-like homeobox gene PagKNAT2/6b could change plant architecture, especially leaf shape, in response to drought stress. However, its regulatory mechanism in leaf development remains unclear. In this work, gene expression analyses of PagKNAT2/6b suggested that PagKNAT2/6b was highly expressed during leaf development. Moreover, the leaf shape changes along the adaxial-abaxial, medial-lateral, and proximal-distal axes caused by the mis-expression of PagKNAT2/6b demonstrated that its overexpression (PagKNAT2/6b OE) and SRDX dominant repression (PagKNAT2/6b SRDX) poplars had an impact on the leaf axial development. The crinkle leaf of PagKNAT2/6b OE was consistent with the differential expression gene PagBOP1/2a (BLADE-ON-PETIOLE), which was the critical gene for regulating leaf development. Further study showed that PagBOP1/2a was directly activated by PagKNAT2/6b through a novel cis-acting element "CTCTT". Together, the PagKNAT2/6b-PagBOP1/2a module regulates poplar leaf morphology by affecting axial development, which provides insights aimed at leaf shape modification for further improving the drought tolerance of woody plants.
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Affiliation(s)
- Yanqiu Zhao
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China; (Y.Z.); (Y.Z.); (W.Z.); (Y.S.); (C.J.); (W.Z.)
| | - Yifan Zhang
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China; (Y.Z.); (Y.Z.); (W.Z.); (Y.S.); (C.J.); (W.Z.)
| | - Weilin Zhang
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China; (Y.Z.); (Y.Z.); (W.Z.); (Y.S.); (C.J.); (W.Z.)
| | - Yangxin Shi
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China; (Y.Z.); (Y.Z.); (W.Z.); (Y.S.); (C.J.); (W.Z.)
| | - Cheng Jiang
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China; (Y.Z.); (Y.Z.); (W.Z.); (Y.S.); (C.J.); (W.Z.)
| | - Xueqin Song
- State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Tree Breeding and Cultivation of the National Forestry and Grassland Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China;
| | - Gerald A. Tuskan
- Center for Bioenergy Innovation, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA;
| | - Wei Zeng
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China; (Y.Z.); (Y.Z.); (W.Z.); (Y.S.); (C.J.); (W.Z.)
| | - Jin Zhang
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China; (Y.Z.); (Y.Z.); (W.Z.); (Y.S.); (C.J.); (W.Z.)
- Correspondence: (J.Z.); (M.L.)
| | - Mengzhu Lu
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China; (Y.Z.); (Y.Z.); (W.Z.); (Y.S.); (C.J.); (W.Z.)
- State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Tree Breeding and Cultivation of the National Forestry and Grassland Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China;
- Correspondence: (J.Z.); (M.L.)
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6
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Wang Y, Li Y, Gong SY, Qin LX, Nie XY, Liu D, Zheng Y, Li XB. GhKNL1 controls fiber elongation and secondary cell wall synthesis by repressing its downstream genes in cotton (Gossypium hirsutum). JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2022; 64:39-55. [PMID: 34796654 DOI: 10.1111/jipb.13192] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 11/16/2021] [Indexed: 06/13/2023]
Abstract
Cotton which produces natural fiber materials for the textile industry is one of the most important crops in the world. Class II KNOX proteins are often considered as transcription factors in regulating plant secondary cell wall (SCW) formation. However, the molecular mechanism of the KNOX transcription factor-regulated SCW synthesis in plants (especially in cotton) remains unclear in details so far. In this study, we show a cotton class II KNOX protein (GhKNL1) as a transcription repressor functioning in fiber development. The GhKNL1-silenced transgenic cotton produced longer fibers with thicker SCWs, whereas GhKNL1 dominant repression transgenic lines displayed the opposite fiber phenotype, compared with controls. Further experiments revealed that GhKNL1 could directly bind to promoters of GhCesA4-2/4-4/8-2 and GhMYB46 for modulating cellulose synthesis during fiber SCW development in cotton. On the other hand, GhKNL1 could also suppress expressions of GhEXPA2D/4A-1/4D-1/13A through binding to their promoters for regulating fiber elongation of cotton. Taken together, these data revealed GhKNL1 functions in fiber elongation and SCW formation by directly repressing expressions of its target genes related to cell elongation and cellulose synthesis. Thus, our data provide an effective clue for potentially improving fiber quality by genetic manipulation of GhKNL1 in cotton breeding.
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Affiliation(s)
- Yao Wang
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
| | - Yang Li
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
| | - Si-Ying Gong
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
| | - Li-Xia Qin
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
| | - Xiao-Ying Nie
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
| | - Dong Liu
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
| | - Yong Zheng
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
| | - Xue-Bao Li
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
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7
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Integration of pluripotency pathways regulates stem cell maintenance in the Arabidopsis shoot meristem. Proc Natl Acad Sci U S A 2020; 117:22561-22571. [PMID: 32839309 PMCID: PMC7486707 DOI: 10.1073/pnas.2015248117] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Pluripotent stem cells are critical in both animal and plant development. Unlike higher animals, plants have unique postembryonic development, which continuously produce organs depending on shoot and root meristems. In the shoot meristem, division of the stem cells in the outermost layers provides the cells for all shoot structures. How those meristem cells are tightly controlled attracted intense studies. Genetic and molecular analyses in Arabidopsis have identified the key transcription factors WUSCHEL (WUS) and SHOOTMERISTEMLESS (STM) as the major regulators of pluripotency in the shoot meristem. Here, the results provide solid evidence showing how those two pluripotency factors WUS and STM coordinate to control shoot meristem cells strictly in plants. In the shoot meristem, both WUSCHEL (WUS) and SHOOT MERISTEMLESS (STM), two transcription factors with overlapping spatiotemporal expression patterns, are essential for maintaining stem cells in an undifferentiated state. Despite their importance, it remains unclear how these two pathways are integrated to coordinate stem cell development. Here, we show that the WUS and STM pathways in Arabidopsis thaliana converge through direct interaction between the WUS and STM proteins. STM binds to the promoter of CLAVATA3 (CLV3) and enhances the binding of WUS to the same promoter through the WUS–STM interaction. Both the heterodimerization and simultaneous binding of WUS and STM at two sites on the CLV3 promoter are required to regulate CLV3 expression, which in turn maintains a constant number of stem cells. Furthermore, the expression of STM depends on WUS, and this WUS-activated STM expression enhances the WUS-mediated stem cell activity. Our data provide a framework for understanding how spatial expression patterns within the shoot meristem are translated into regulatory units of stem cell homeostasis.
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8
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Huang B, Huang D, Hong Z, Owie SO, Wu W. Genetic analysis reveals four interacting loci underlying awn trait diversity in barley (Hordeum vulgare). Sci Rep 2020; 10:12535. [PMID: 32719425 PMCID: PMC7385259 DOI: 10.1038/s41598-020-69335-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2020] [Accepted: 07/10/2020] [Indexed: 11/09/2022] Open
Abstract
Barley (Hordeum vulgare) awns contribute to grain yield, but the genetic basis of awn development remains largely unclear. Five barley lines differing in awn traits and row types were used to create four F2 populations. Genetic analyses revealed that four pairs of genes were involved in awn development: A/a (awnless/awned), B/b (awnless/awned), H/h (hooded/straight), and L/l (long/short). Of these four loci, A, H and L functioned on both central rows (CR) and lateral rows (LR) of the barley spikes, while B exhibited effect only on LR. A and B had duplicate effects on LR, and both showed dominant epistasis to loci H and L, whereas H was epistatic to L. Meanwhile, A and B were found to be genetically linked, with a row-type locus V located between them. The genetic distances of A-V and B-V were estimated to be 9.6 and 7.7 cM, respectively. Literature search suggested that A, H and V may correspond to the reported Lks1, Kap1 and Vrs1, respectively, whereas B is a novel gene specifically controlling awn development on LR, designated as Lsa1 for lateral spikelet awnless 1. The only barley homolog of wheat awn inhibitor gene B1, HORVU2Hr1G077570, is a potential candidate of Lsa1.
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Affiliation(s)
- Biguang Huang
- Key Laboratory for Genetics, Breeding and Multiple Utilization of Crops, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China. .,Fujian Collegiate Key Laboratory of Applied Plant Genetics, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China. .,Department of Plant Sciences, University of Idaho, Moscow, ID, 83844, USA.
| | - Daiqing Huang
- Aquatic and Crop Resource Development, National Research Council of Canada, Saskatoon, SK, S7N 0W9, Canada
| | - Zonglie Hong
- Department of Plant Sciences, University of Idaho, Moscow, ID, 83844, USA
| | - Swithin Omosuwa Owie
- Key Laboratory for Genetics, Breeding and Multiple Utilization of Crops, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China.,Fujian Collegiate Key Laboratory of Applied Plant Genetics, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China
| | - Weiren Wu
- Key Laboratory for Genetics, Breeding and Multiple Utilization of Crops, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China. .,Fujian Key Laboratory of Crop Breeding by Design, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China.
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9
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Zhao M, Li C, Ma X, Xia R, Chen J, Liu X, Ying P, Peng M, Wang J, Shi CL, Li J. KNOX protein KNAT1 regulates fruitlet abscission in litchi by repressing ethylene biosynthetic genes. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:4069-4082. [PMID: 32227110 DOI: 10.1093/jxb/eraa162] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2020] [Accepted: 03/27/2020] [Indexed: 05/25/2023]
Abstract
Abscission is triggered by multiple environmental and developmental cues, including endogenous plant hormones. KNOTTED-LIKE HOMEOBOX (KNOX) transcription factors (TFs) play an important role in controlling abscission in plants. However, the underlying molecular mechanism of KNOX TFs in abscission is largely unknown. Here, we identified LcKNAT1, a KNOTTED-LIKE FROM ARABIDOPSIS THALIANA1 (KNAT1)-like protein from litchi, which regulates abscission by modulating ethylene biosynthesis. LcKNAT1 is expressed in the fruit abscission zone and its expression decreases during fruitlet abscission. Furthermore, the expression of the ethylene biosynthetic genes LcACS1, LcACS7, and LcACO2 increases in the fruit abscission zone, in parallel with the emission of ethylene in fruitlets. In vitro and in vivo assays revealed that LcKNAT1 inhibits the expression of LcACS/ACO genes by directly binding to their promoters. Moreover, ectopic expression of LcKNAT1 represses flower abscission in tomatoes. Transgenic plants expressing LcKNAT1 also showed consistently decreased expression of ACS/ACO genes. Collectively, these results indicate that LcKNAT1 represses abscission via the negative regulation of ethylene biosynthesis.
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Affiliation(s)
- Minglei Zhao
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, China Litchi Research Center, South China Agricultural University, Guangzhou, China
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Postharvest Science of Fruits and Vegetables, College of Horticulture, South China Agricultural University, Guangzhou, China
| | - Caiqin Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, China Litchi Research Center, South China Agricultural University, Guangzhou, China
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
| | - Xingshuai Ma
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, China Litchi Research Center, South China Agricultural University, Guangzhou, China
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
| | - Rui Xia
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, China Litchi Research Center, South China Agricultural University, Guangzhou, China
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
| | - Jianye Chen
- Guangdong Provincial Key Laboratory of Postharvest Science of Fruits and Vegetables, College of Horticulture, South China Agricultural University, Guangzhou, China
| | - Xuncheng Liu
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Peiyuan Ying
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, China Litchi Research Center, South China Agricultural University, Guangzhou, China
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
| | - Manjun Peng
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, China Litchi Research Center, South China Agricultural University, Guangzhou, China
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
| | - Jun Wang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, China Litchi Research Center, South China Agricultural University, Guangzhou, China
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
| | - Chun-Lin Shi
- Section of Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, Oslo, Norway
| | - Jianguo Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, China Litchi Research Center, South China Agricultural University, Guangzhou, China
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
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10
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Azarakhsh M, Rumyantsev AM, Lebedeva MA, Lutova LA. Cytokinin biosynthesis genes expressed during nodule organogenesis are directly regulated by the KNOX3 protein in Medicago truncatula. PLoS One 2020; 15:e0232352. [PMID: 32353031 PMCID: PMC7192382 DOI: 10.1371/journal.pone.0232352] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 04/14/2020] [Indexed: 11/20/2022] Open
Abstract
Cytokinin is an important regulator of symbiotic nodule development. Recently, KNOTTED1-LIKE HOMEOBOX 3 transcription factor (TF) was shown to regulate symbiotic nodule development possibly via the activation of cytokinin biosynthesis genes. However, the direct interaction between the KNOX3 TF and its target genes has not been investigated up to date. Here, using EMSA analysis and SPR-based assay, we found that MtKNOX3 homeodomain directly binds to the regulatory sequences of the MtLOG1, MtLOG2, and MtIPT3 genes involved in nodulation in Medicago truncatula. Moreover, we showed that MtLOG2 and MtIPT3 expression patterns partially overlap with MtKNOX3 expression in developing nodules as it was shown by promoter:GUS analysis. Our data suggest that MtKNOX3 TF may directly activate the MtLOG1, MtLOG2, and MtIPT3 genes during nodulation thereby increasing cytokinin biosynthesis in developing nodules.
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Affiliation(s)
- Mahboobeh Azarakhsh
- Department of Genetics and Biotechnology, Saint Petersburg State University, Saint Petersburg, Russia
- Cell and Molecular Biology Department, Kosar University of Bojnord, Bojnord, North Khorasan Province, Iran
| | - Andrey M Rumyantsev
- Department of Genetics and Biotechnology, Saint Petersburg State University, Saint Petersburg, Russia
| | - Maria A Lebedeva
- Department of Genetics and Biotechnology, Saint Petersburg State University, Saint Petersburg, Russia
| | - Lyudmila A Lutova
- Department of Genetics and Biotechnology, Saint Petersburg State University, Saint Petersburg, Russia
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11
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Feng H, Li X, Chen H, Deng J, Zhang C, Liu J, Wang T, Zhang X, Dong J. GhHUB2, a ubiquitin ligase, is involved in cotton fiber development via the ubiquitin-26S proteasome pathway. JOURNAL OF EXPERIMENTAL BOTANY 2018; 69:5059-5075. [PMID: 30053051 PMCID: PMC6184758 DOI: 10.1093/jxb/ery269] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 07/12/2018] [Indexed: 05/02/2023]
Abstract
Cotton fibers, which are extremely elongated single cells of epidermal seed trichomes and have highly thickened cell walls, constitute the most important natural textile material worldwide. However, the regulation of fiber development is not well understood. Here, we report that GhHUB2, a functional homolog of AtHUB2, controls fiber elongation and secondary cell wall (SCW) deposition. GhHUB2 is ubiquitously expressed, including within fibers. Overexpression of GhHUB2 in cotton increased fiber length and SCW thickness, while RNAi knockdown of GhHUB2 resulted in shortened fibers and thinner cell walls. We found that GhHUB2 interacted with GhKNL1, a transcriptional repressor predominantly expressed in developing fibers, and that GhHUB2 ubiquitinated and degraded GhKNL1 via the ubiquitin-26S proteasome pathway. GhHUB2 negatively regulated GhKNL1 protein levels and lead to the disinhibition of genes such as GhXTH1, Gh1,3-β-G, GhCesA4, GhAGP4, GhCTL1, and GhCOBL4, thus promoting fiber elongation and enhancing SCW biosynthesis. We found that GhREV-08, a transcription factor that participates in SCW deposition and auxin signaling pathway, was a direct target of GhKNL1. In conclusion, our study uncovers a novel function of HUB2 in plants in addition to its monoubiquitination of H2B. Moreover, we provide evidence for control of the fiber development by the ubiquitin-26S proteasome pathway.
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Affiliation(s)
- Hao Feng
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Xin Li
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Hong Chen
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Jie Deng
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Chaojun Zhang
- State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, China
| | - Ji Liu
- State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, China
| | - Tao Wang
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Xueyan Zhang
- State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, China
| | - Jiangli Dong
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
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12
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Liu Y, You S, Taylor-Teeples M, Li WL, Schuetz M, Brady SM, Douglas CJ. BEL1-LIKE HOMEODOMAIN6 and KNOTTED ARABIDOPSIS THALIANA7 interact and regulate secondary cell wall formation via repression of REVOLUTA. THE PLANT CELL 2014; 26:4843-61. [PMID: 25490916 PMCID: PMC4311193 DOI: 10.1105/tpc.114.128322] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 11/04/2014] [Accepted: 11/17/2014] [Indexed: 05/17/2023]
Abstract
The TALE homeodomain transcription factor KNOTTED ARABIDOPSIS THALIANA7 (KNAT7) is part of a regulatory network governing the commitment to secondary cell wall biosynthesis of Arabidopsis thaliana, where it contributes to negative regulation of this process. Here, we report that BLH6, a BELL1-LIKE HOMEODOMAIN protein, specifically interacts with KNAT7, and this interaction influences secondary cell wall development. BLH6 is a transcriptional repressor, and BLH6-KNAT7 physical interaction enhances KNAT7 and BLH6 repression activities. The overlapping expression patterns of BLH6 and KNAT7 and phenotypes of blh6, knat7, and blh6 knat7 loss-of-function mutants are consistent with the existence of a BLH6-KNAT7 heterodimer that represses commitment to secondary cell wall biosynthesis in interfascicular fibers. BLH6 and KNAT7 overexpression results in thinner interfascicular fiber secondary cell walls, phenotypes that are dependent on the interacting partner. A major impact of the loss of BLH6 and KNAT7 function is enhanced expression of the homeodomain-leucine zipper transcription factor REVOLUTA/INTERFASCICULAR FIBERLESS1 (REV/IFL1). BLH6 and KNAT7 bind to the REV promoter and repress REV expression, while blh6 and knat7 interfascicular fiber secondary cell wall phenotypes are suppressed in blh6 rev and knat7 rev double mutants, suggesting that BLH6/KNAT7 signaling acts through REV as a direct target.
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Affiliation(s)
- Yuanyuan Liu
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Shijun You
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Mallorie Taylor-Teeples
- Department of Plant Biology, UC Davis, Davis, California 95616 Genome Center, UC Davis, Davis, California 95616
| | - Wenhua L Li
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Mathias Schuetz
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Siobhan M Brady
- Department of Plant Biology, UC Davis, Davis, California 95616 Genome Center, UC Davis, Davis, California 95616
| | - Carl J Douglas
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
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13
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Wen BQ, Xing MQ, Zhang H, Dai C, Xue HW. Rice homeobox transcription factor HOX1a positively regulates gibberellin responses by directly suppressing EL1. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2011; 53:869-78. [PMID: 21951842 DOI: 10.1111/j.1744-7909.2011.01075.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Homeobox transcription factors are involved in various aspects of plant development, including maintenance of the biosynthesis and signaling pathways of different hormones. However, few direct targets of homeobox proteins have been identified. We here show that overexpression of rice homeobox gene HOX1a resulted in enhanced gibberellin (GA) response, indicating a positive effect of HOX1a in GA signaling. HOX1a is induced by GA and encodes a homeobox transcription factor with transcription repression activity. In addition, HOX1a suppresses the transcription of early flowering1 (EL1), a negative regulator of GA signaling, and further electrophoretic mobility shift assay and chromatin immunoprecipitation analysis revealed that HOX1a directly bound to the promoter region of EL1 to suppress its expression and stimulate GA signaling. These results demonstrate that HOX1a functions as a positive regulator of GA signaling by suppressing EL1, providing informative hints on the study of GA signaling.
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Affiliation(s)
- Bi-Qing Wen
- National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institute for Biological Sciences, the Chinese Academy of Sciences, Shanghai 200032, China
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14
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Spinelli SV, Martin AP, Viola IL, Gonzalez DH, Palatnik JF. A mechanistic link between STM and CUC1 during Arabidopsis development. PLANT PHYSIOLOGY 2011; 156:1894-904. [PMID: 21685178 PMCID: PMC3149926 DOI: 10.1104/pp.111.177709] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Accepted: 06/10/2011] [Indexed: 05/19/2023]
Abstract
The KNOXI transcription factor SHOOT MERISTEMLESS (STM) is required to establish and maintain the Arabidopsis (Arabidopsis thaliana) apical meristem, yet little is known about its direct targets. Using different approaches we demonstrate that the induction of STM causes a significant up-regulation of the organ boundary gene CUP SHAPED COTYLEDON1 (CUC1), which is specific and independent of other meristem regulators. We further show that the regulation of CUC1 by STM is direct and identify putative binding sites in its promoter. Continuous expression of STM in Arabidopsis leaf primordia also causes the activation of CUC2-3, as well as microRNA MIR164a, which provides a negative feedback loop by posttranscriptionally regulating CUC1 and CUC2. The results bring new insights into the mechanistic links between KNOXI and CUC transcription factors and contribute to the understanding of the regulatory network controlled by STM.
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15
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Wang R, Guan P, Chen M, Xing X, Zhang Y, Crawford NM. Multiple regulatory elements in the Arabidopsis NIA1 promoter act synergistically to form a nitrate enhancer. PLANT PHYSIOLOGY 2010; 154:423-32. [PMID: 20668061 PMCID: PMC2938143 DOI: 10.1104/pp.110.162586] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Accepted: 07/16/2010] [Indexed: 05/19/2023]
Abstract
To accommodate fluctuating nutrient levels in the soil, plants modulate their metabolism and root development via signaling mechanisms that rapidly reprogram the plant transcriptome. In the case of nitrate, over 1,000 genes are induced or repressed within minutes of nitrate exposure. To identify cis-regulatory elements that mediate these responses, an enhancer screen was performed in transgenic Arabidopsis (Arabidopsis thaliana) plants. A 1.8-kb promoter fragment from the nitrate reductase gene NIA1 was identified that acts as a nitrate enhancer when fused to a 35S minimal promoter. Enhancer activity was localized to a 180-bp fragment, and this activity could be enhanced by the addition of a 131-bp fragment from the nitrite reductase promoter. A promoter construct containing the 180- and 131-bp fragments was also induced by nitrite and repressed by ammonium, indicating that it was responsive to multiple nitrogen signals. To identify specific regulatory elements within the 180-bp NIA1 fragment, a transient expression system using agroinfiltration of Nicotiana benthamiana was developed. Deletion analysis identified three elements corresponding to predicted binding motifs for homeodomain/E-box, Myb, and Alfin1 transcription factors. A fully active promoter showing nitrate and nitrite enhancer activity equivalent to that of the wild-type 180-bp fragment could be built from these three elements if the spacing between the homeodomain/E-box and Myb-Alfin1 sites was equivalent to that of the native promoter. These findings were validated in transgenic Arabidopsis plants and identify a cis-regulatory module containing three elements that comprise a nitrate enhancer in the NIA1 promoter.
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Affiliation(s)
| | | | | | | | | | - Nigel M. Crawford
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093–0116 (R.W., P.G., X.X., N.M.C.); State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China (M.C.); College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China (Y.Z.)
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16
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Takano S, Niihama M, Smith HMS, Tasaka M, Aida M. gorgon, a Novel Missense Mutation in the SHOOT MERISTEMLESS Gene, Impairs Shoot Meristem Homeostasis in Arabidopsis. ACTA ACUST UNITED AC 2010; 51:621-34. [DOI: 10.1093/pcp/pcq028] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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17
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Bolduc N, Hake S. The maize transcription factor KNOTTED1 directly regulates the gibberellin catabolism gene ga2ox1. THE PLANT CELL 2009; 21:1647-58. [PMID: 19567707 PMCID: PMC2714931 DOI: 10.1105/tpc.109.068221] [Citation(s) in RCA: 196] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Revised: 05/31/2009] [Accepted: 06/08/2009] [Indexed: 05/18/2023]
Abstract
KNOTTED1 (KN1)-like homeobox (KNOX) transcription factors are involved in the establishment and maintenance of plant meristems; however, few direct targets of KNOX proteins have been recognized. Using a combination of double mutant analysis and biochemistry, we found that in maize (Zea mays), KN1 negatively modulates the accumulation of gibberellin (GA) through the control of ga2ox1, which codes for an enzyme that inactivates GA. The ga2ox1 mRNA level is elevated in immature leaves of dominant KNOX mutants and downregulated in reproductive meristems of the null allele kn1-e1. KN1 binds in vivo to an intron of ga2ox1 through a cis-regulatory element containing two TGAC motifs. VP16-KN1 activates transcription in planta from a chimeric promoter containing this binding site. The domains of expression of kn1 and ga2ox1 mRNAs overlap at the base of the shoot apical meristem and the base of newly initiated leaves, suggesting that KN1-mediated activation of ga2ox1 maintains a boundary between meristem cell identity and rapidly elongating cells of the shoot. The KN1 binding site is conserved in ga2ox1 genes of different grasses, suggesting that the local regulation of bioactive GA levels through KNOX proteins is a common theme in grasses.
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Affiliation(s)
- Nathalie Bolduc
- Plant Gene Expression Center, U.S. Department of Agriculture-Agricultural Research Service, University of California, Albany, California 94710, USA
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18
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Lee JH, Lin H, Joo S, Goodenough U. Early sexual origins of homeoprotein heterodimerization and evolution of the plant KNOX/BELL family. Cell 2008; 133:829-40. [PMID: 18510927 DOI: 10.1016/j.cell.2008.04.028] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Revised: 04/03/2008] [Accepted: 04/21/2008] [Indexed: 11/30/2022]
Abstract
Developmental mechanisms that yield multicellular diversity are proving to be well conserved within lineages, generating interest in their origins in unicellular ancestors. We report that molecular regulation of the haploid-diploid transition in Chlamydomonas, a unicellular green soil alga, shares common ancestry with differentiation pathways in land plants. Two homeoproteins, Gsp1 and Gsm1, contributed by gametes of plus and minus mating types respectively, physically interact and translocate from the cytosol to the nucleus upon gametic fusion, initiating zygote development. Their ectopic expression activates zygote development in vegetative cells and, in a diploid background, the resulting zygotes undergo a normal meiosis. Gsm1/Gsp1 dyads share sequence homology with and are functionally related to KNOX/BELL dyads regulating stem-cell (meristem) specification in land plants. We propose that combinatorial homeoprotein-based transcriptional control, a core feature of the fungal/animal radiation, may have originated in a sexual context and enabled the evolution of land-plant body plans.
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Affiliation(s)
- Jae-Hyeok Lee
- Department of Biology, Washington University, St. Louis, MO 63130, USA
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19
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Bolduc N, Hake S, Jackson D. Dual functions of the KNOTTED1 homeodomain: sequence-specific DNA binding and regulation of cell-to-cell transport. Sci Signal 2008; 1:pe28. [PMID: 18544748 DOI: 10.1126/scisignal.123pe28] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Homeodomain proteins are well-characterized developmental regulators that control expression of target genes through sequence-specific DNA binding. The homeodomain forms a trihelical structure, with the third helix conferring specific interactions with the DNA major groove. A specific class of plant homeodomain proteins, called KNOX [KNOTTED1 (KN1)-like homeobox], also has the ability to signal between cells by directly trafficking through intercellular channels called plasmodesmata. Trafficking is mediated by a signal that is also contained within the homeodomain. Movement protein binding protein 2C was identified as a protein that interacts with the KN1 homeodomain and regulates the cell-to-cell trafficking of KN1 by sequestering the protein on microtubules. Therefore, KN1 has multiple potential cellular addresses, each of which is conferred by its homeodomain.
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Affiliation(s)
- Nathalie Bolduc
- Plant Gene Expression Center, 800 Buchanan Street, Albany, CA 94710, USA
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20
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Viola IL, Gonzalez DH. Interaction of the BELL-like protein ATH1 with DNA: role of homeodomain residue 54 in specifying the different binding properties of BELL and KNOX proteins. Biol Chem 2006; 387:31-40. [PMID: 16497162 DOI: 10.1515/bc.2006.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We have studied the interaction of the BELL-like Arabidopsis homeodomain protein ATH1 with DNA. Analysis of oligonucleotides selected by the ATH1 homeodomain from a random mixture suggests that ATH1 preferentially binds the sequence TGACAGGT. Single nucleotide replacements at positions 2 or 3 of this sequence abolish binding, while changes at position 4 are more tolerated. Changes outside this core differentially affect binding, depending on the position. Hydroxyl radical footprinting and missing nucleoside experiments showed that ATH1 interacts with a 7-bp region of the strand carrying the GAC core. On the other strand, protection was observed over a 7-bp region, comprising one additional nucleotide complementary to T in position 1. A comparative analysis of the binding preferences of the homeodomains of ATH1 and STM (a KNOX homeodomain protein) indicated that they bind similar sequences, but with differences in affinity and specificity. The decreased affinity displayed by the ATH1 homeodomain correlates with the presence of valine (instead of lysine as in STM) at position 54. This difference also explains the decreased and increased selectivities, respectively, at positions 4 and 5. Our results point to an essential role of residue 54 in determining the different binding properties of BELL and KNOX homeodomains.
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Affiliation(s)
- Ivana L Viola
- Cátedra de Biología Celular y Molecular, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, CC 242 Paraje El Pozo, 3000 Santa Fe, Argentina
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21
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Steffens NO, Galuschka C, Schindler M, Bülow L, Hehl R. AthaMap web tools for database-assisted identification of combinatorial cis-regulatory elements and the display of highly conserved transcription factor binding sites in Arabidopsis thaliana. Nucleic Acids Res 2005; 33:W397-402. [PMID: 15980498 PMCID: PMC1160156 DOI: 10.1093/nar/gki395] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2005] [Revised: 03/11/2005] [Accepted: 03/11/2005] [Indexed: 11/14/2022] Open
Abstract
The AthaMap database generates a map of cis-regulatory elements for the Arabidopsis thaliana genome. AthaMap contains more than 7.4 x 10(6) putative binding sites for 36 transcription factors (TFs) from 16 different TF families. A newly implemented functionality allows the display of subsets of higher conserved transcription factor binding sites (TFBSs). Furthermore, a web tool was developed that permits a user-defined search for co-localizing cis-regulatory elements. The user can specify individually the level of conservation for each TFBS and a spacer range between them. This web tool was employed for the identification of co-localizing sites of known interacting TFs and TFs containing two DNA-binding domains. More than 1.8 x 10(5) combinatorial elements were annotated in the AthaMap database. These elements can also be used to identify more complex co-localizing elements consisting of up to four TFBSs. The AthaMap database and the connected web tools are a valuable resource for the analysis and the prediction of gene expression regulation at http://www.athamap.de.
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Affiliation(s)
- Nils Ole Steffens
- Institut für Genetik, Technische Universität BraunschweigSpielmannstraße 7, D-38106 Braunschweig, Germany
| | - Claudia Galuschka
- Institut für Genetik, Technische Universität BraunschweigSpielmannstraße 7, D-38106 Braunschweig, Germany
| | - Martin Schindler
- Institut für Genetik, Technische Universität BraunschweigSpielmannstraße 7, D-38106 Braunschweig, Germany
| | - Lorenz Bülow
- Institut für Genetik, Technische Universität BraunschweigSpielmannstraße 7, D-38106 Braunschweig, Germany
| | - Reinhard Hehl
- Institut für Genetik, Technische Universität BraunschweigSpielmannstraße 7, D-38106 Braunschweig, Germany
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22
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Abstract
knox genes encode homeodomain-containing transcription factors that are required for meristem maintenance and proper patterning of organ initiation. In plants with simple leaves, knox genes are expressed exclusively in the meristem and stem, but in dissected leaves, they are also expressed in leaf primordia, suggesting that they may play a role in the diversity of leaf form. This hypothesis is supported by the intriguing phenotypes found in gain-of-function mutations where knox gene misexpression affects leaf and petal shape. Similar phenotypes are also found in recessive mutations of genes that function to negatively regulate knox genes. KNOX proteins function as heterodimers with other homeodomains in the TALE superclass. The gibberellin and lignin biosynthetic pathways are known to be negatively regulated by KNOX proteins, which results in indeterminate cell fates.
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Affiliation(s)
- Sarah Hake
- Plant Gene Expression Center, USDA-ARS and University of California, Albany, CA 94710, USA.
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23
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Tioni MF, Viola IL, Chan RL, Gonzalez DH. Site-directed mutagenesis and footprinting analysis of the interaction of the sunflower KNOX protein HAKN1 with DNA. FEBS J 2004. [DOI: 10.1111/j.1432-1033.2005.04402.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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24
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Chen H, Banerjee AK, Hannapel DJ. The tandem complex of BEL and KNOX partners is required for transcriptional repression of ga20ox1. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 38:276-84. [PMID: 15078330 DOI: 10.1111/j.1365-313x.2004.02048.x] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Summary Two interacting three amino acid loop extension (TALE) proteins of potato, StBEL5 (Solanum tuberosom BEL 5) and POTH1 (potato homeobox 1), mediate developmental processes by regulating phytohormone levels. Overexpression of either partner alone increased tuber yields by lowering gibberellin (GA) levels and increasing cytokinins. Gel shift assays demonstrated that StBEL5 and POTH1 bind to the regulatory region of ga20 oxidase1 (ga20ox1) from potato, a gene encoding a key enzyme in the GA biosynthetic pathway. In tandem, StBEL5 and POTH1 had a greater binding affinity for the ga20ox1 promoter than either protein alone. The StBEL5-POTH1 heterodimer bound specifically to a composite 10-bp sequence, containing two TGAC cores. Using a transcription assay, StBEL5 and POTH1 suppressed the activity of the ga20ox1 promoter by more than 50%. Dominant negative constructs containing the protein-binding domains of StBEL5 or POTH1 blocked the repression activity of StBEL5 or POTH1, respectively. The mutated ga20ox1 promoter that could be bound by the StBEL5 or POTH1 proteins individually but not by the StBEL5-POTH1 heterodimer also abolished the repression activity of StBEL5, POTH1, and the StBEL5-POTH1 heterodimer. These results indicate that the tandem interaction of StBEL5 and POTH1 is essential for regulation of the expression of their target gene.
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Affiliation(s)
- Hao Chen
- Interdepartmental Plant Physiology Major, Iowa State University, Ames, IA 50011-1100, USA
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25
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Steffens NO, Galuschka C, Schindler M, Bülow L, Hehl R. AthaMap: an online resource for in silico transcription factor binding sites in the Arabidopsis thaliana genome. Nucleic Acids Res 2004; 32:D368-72. [PMID: 14681436 PMCID: PMC308752 DOI: 10.1093/nar/gkh017] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2003] [Revised: 09/04/2003] [Accepted: 09/04/2003] [Indexed: 11/14/2022] Open
Abstract
Gene expression is controlled mainly by the binding of transcription factors to regulatory sequences. To generate a genomic map for regulatory sequences, the Arabidopsis thaliana genome was screened for putative transcription factor binding sites. Using publicly available data from the TRANSFAC database and from publications, alignment matrices for 23 transcription factors of 13 different factor families were used with the pattern search program Patser to determine the genomic positions of more than 2.4 x 10(6) putative binding sites. Due to the dense clustering of genes and the observation that regulatory sequences are not restricted to upstream regions, the prediction of binding sites was performed for the whole genome. The genomic positions and the underlying data were imported into the newly developed AthaMap database. This data can be accessed by positional information or the Arabidopsis Genome Initiative identification number. Putative binding sites are displayed in the defined region. Data on the matrices used and on the thresholds applied in these screens are given in the database. Considering the high density of sites it will be a valuable resource for generating models on gene expression regulation. The data are available at http://www.athamap.de.
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Affiliation(s)
- Nils Ole Steffens
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany
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26
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Smith HMS, Boschke I, Hake S. Selective interaction of plant homeodomain proteins mediates high DNA-binding affinity. Proc Natl Acad Sci U S A 2002; 99:9579-84. [PMID: 12093897 PMCID: PMC123183 DOI: 10.1073/pnas.092271599] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2002] [Accepted: 05/06/2002] [Indexed: 11/18/2022] Open
Abstract
Understanding molecular mechanisms that control cell fate in the shoot apical meristem is a fundamental question in plant development. Genetic and molecular studies demonstrate that maize KNOTTED1 (KN1) of the TALE (3-aa acid loop extension) class of homeodomain (HD) proteins is involved in shoot apical meristem function. We show that KN1 interacts with knotted interacting protein (KIP), a BEL1-like TALE HD protein. Interaction between KN1 and KIP is mediated by conserved domains in the N termini of both proteins. The KN1 DNA-binding sequence, TGACAG(G/C)T, was biochemically identified, and in vitro DNA-binding assays show that individually KN1 and the HD of KIP bind specifically to this motif with low affinity. The KN1-KIP complex, however, binds specifically to this DNA-binding motif with high affinity, indicating that the association of KN1 and KIP may function in transcriptional regulation.
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Affiliation(s)
- Harley M S Smith
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
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27
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Ito Y, Hirochika H, Kurata N. Organ-specific alternative transcripts of KNOX family class 2 homeobox genes of rice. Gene 2002; 288:41-7. [PMID: 12034492 DOI: 10.1016/s0378-1119(02)00460-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We identified three genes (HOS58, HOS59 and HOS66) of rice (Oryza sativa), which encode predicted proteins with the KNOX family class 2 homeodomain. These proteins contain three conserved domains, the KNOX domain, ELK domain and homeodomain, from an N-terminus to a C-terminus. In addition to similarity of predicted amino acid sequences, these genes showed a similar exon/intron structure. cDNA cloning and reverse transcription-polymerase chain reaction analyses of these genes indicated tissue-specific expression of alternative transcripts. The expression of the longer mRNAs of HOS58 (HOS58L) and HOS59L was detected in all organs examined such as roots, leaf blades, leaf sheaths, flowers and calli, whereas the shorter mRNAs of HOS58 (HOS58S) and HOS59S were expressed in leaf blades, leaf sheaths and flowers. The expression of HOS66L was detected in roots, leaf blades, leaf sheaths and flowers, whereas the expression of HOS66S was detected in roots and flowers. The alternative transcripts of HOS66 arose by use of alternative transcription start sites. The longer transcripts contained an exon 1 which encodes an alanine/glycine-rich region, whereas the shorter ones lacked it. These results suggest that the expression of the alternative transcripts is organ-specific, and their products have different degrees of abilities for activation or repression of transcription.
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Affiliation(s)
- Yukihiro Ito
- Plant Genetics Laboratory, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan
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28
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Ito Y, Eiguchi M, Kurata N. KNOX homeobox genes are sufficient in maintaining cultured cells in an undifferentiated state in rice. Genesis 2001; 30:231-8. [PMID: 11536429 DOI: 10.1002/gene.1069] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We produced transgenic rice calli, which constitutively express each of four KNOX family class 1 homeobox genes of rice, OSH1, OSH16, OSH15, and OSH71, and found that constitutive and ectopic expression of such genes inhibits normal regeneration from transformed calli, which showed continuous growth around their shoot-regenerating stages. Transgenic calli transferred onto regeneration medium began to display green spots, a sign of regeneration, but most of the transformants continued to propagate green spots at given stages. In the normal shoot-regeneration process of calli, expression of endogenous OSH1 was restricted in presumptive shoot-regenerating regions of calli and not observed in other areas. This restricted expression pattern should be required for further differentiation of the regenerating shoots. Thus our present results support the proposed function that KNOX family class 1 homeobox genes play a role in the formation and maintenance of the undetermined meristematic state of cells.
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MESH Headings
- Cell Differentiation/genetics
- Cells, Cultured
- Cloning, Molecular
- Conserved Sequence/genetics
- Gene Expression Regulation, Plant
- Genes, Homeobox/genetics
- Genes, Plant/genetics
- Homeodomain Proteins/genetics
- Homeodomain Proteins/metabolism
- In Situ Hybridization
- Meristem/cytology
- Meristem/genetics
- Meristem/growth & development
- Meristem/metabolism
- Oryza/cytology
- Oryza/genetics
- Oryza/growth & development
- Oryza/metabolism
- Phenotype
- Plant Proteins/genetics
- Plant Proteins/metabolism
- Plants, Genetically Modified
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Plant/genetics
- RNA, Plant/metabolism
- Trans-Activators/genetics
- Trans-Activators/metabolism
- Transformation, Genetic
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Affiliation(s)
- Y Ito
- Plant Genetics Laboratory, National Institute of Genetics, Shizuoka-ken, Japan
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29
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Sakamoto T, Kamiya N, Ueguchi-Tanaka M, Iwahori S, Matsuoka M. KNOX homeodomain protein directly suppresses the expression of a gibberellin biosynthetic gene in the tobacco shoot apical meristem. Genes Dev 2001; 15:581-90. [PMID: 11238378 PMCID: PMC312643 DOI: 10.1101/gad.867901] [Citation(s) in RCA: 297] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2000] [Accepted: 01/08/2001] [Indexed: 11/25/2022]
Abstract
To identify genes targeted by the tobacco KNOX homeodomain protein, Nicotiana tabacum homeobox 15 (NTH15), we have generated an inducible system using the human glucocorticoid receptor. In this system, steroid treatment strictly induced NTH15 function and immediately suppressed the expression of a gibberellin (GA) biosynthetic gene encoding GA 20-oxidase (Ntc12) and also resulted in a decrease in bioactive GA levels. The repression of Ntc12 was observed even when indirect effects were blocked by cycloheximide. NTH15 mRNA was present in corpus cells of the shoot apical meristem (SAM), whereas Ntc12 mRNA was observed in leaf primordia and rib meristem but not in the corpus. Recombinant NTH15 protein strongly bound to a 5-bp dyadsymmetric sequence, GTGAC, in the first intron of Ntc12 in vitro. Mutation of this sequence in the Ntc12 gene abolished the NTH15-dependent suppression of Ntc12 in the corpus of the SAM. Our results indicate that NTH15 directly represses Ntc12 expression in the corpus of the wild-type SAM to maintain the indeterminate state of corpus cells. The suppression of NTH15 within cells at the flanks of the SAM permits GA biosynthesis, which promotes organized cell proliferation and consequently induces the determination of cell fate.
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Affiliation(s)
- T Sakamoto
- Institute of Agriculture and Forestry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
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30
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Tejada ML, Jia Z, May D, Deeley RG. Determinants of the DNA-binding specificity of the Avian homeodomain protein, AKR. DNA Cell Biol 1999; 18:791-804. [PMID: 10541438 DOI: 10.1089/104454999314935] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AKR (Avian Knotted-Related) was the first example of a vertebrate homeodomain protein with a highly divergent Ile residue at position 50 of the DNA-recognition helix. The protein was cloned from a liver cDNA expression library of a day-9 chick embryo by virtue of its ability to bind to the F' site in the proximal promoter of the avian apoVLDLII gene. Expression of the apoVLDLII gene is completely estrogen dependent, and mutation or deletion of the F' site decreases estrogen inducibility 5- to 10-fold. Subsequent data indicated that AKR is capable of repressing the hormone responsiveness of the apoVLDLII promoter, specifically through binding to F'. Involvement of the F' site in the hormone-dependent activation of apoVLDLII gene expression, as well as AKR-mediated repression, strongly suggests that both positive and negative regulatory factors interact with this site. Although several mammalian proteins have now been isolated whose homeodomains share many of the structural features of AKR, including the Ile at position 50, little is known of their functions in vivo or the identities of the genes they regulate. Consequently, the elements through which they exert their effects and the structural determinants of their binding specificities remain largely uncharacterized. In this study, we defined the sequence specificity of binding by AKR using polymerase chain reaction-assisted optimal site selection and determined the affinity with which the protein binds to both the optimized site and the F' site. Additionally, we generated a three-dimensional model of the AKR homeodomain binding to its optimized site and probed the validity of the model by examining the consequences of mutating amino acid residues in recognition helix 3 and the N-terminal arm on the binding specificity of the homeodomain. Finally, we present evidence that the F' site itself may act as an estrogen response element (ERE) when in the vicinity of imperfect or canonical EREs and that AKR can repress hormone inducibility mediated via this site.
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Affiliation(s)
- M L Tejada
- Department of Biochemistry, Queen's University, Kingston, Ontario, Canada
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31
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Muehlbauer GJ, Fowler JE, Girard L, Tyers R, Harper L, Freeling M. Ectopic expression of the maize homeobox gene liguleless3 alters cell fates in the leaf. PLANT PHYSIOLOGY 1999; 119:651-62. [PMID: 9952462 PMCID: PMC32143 DOI: 10.1104/pp.119.2.651] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/1998] [Accepted: 11/03/1998] [Indexed: 05/19/2023]
Abstract
The semidominant mutation Liguleless3-O (Lg3-O) causes a blade-to-sheath transformation at the midrib region of the maize (Zea mays L.) leaf. We isolated a full-length lg3 cDNA containing a knotted1-like family homeobox. Six Lg3-O partial revertant alleles caused by insertion of a Mutator (Mu) transposon and two deletion derivatives were isolated and used to verify that our knotted1-like cDNA corresponds to the LG3 message. In wild-type plants the LG3 mRNA is expressed in apical regions but is not expressed in leaves. In mutant plants harboring any of three dominant lg3 alleles (Lg3-O, -Mlg, and -347), LG3 mRNA is expressed in leaf sheath tissue, indicating that the Lg3 phenotype is due to ectopic expression of the gene. The Lg3-O revertant alleles represent two classes of Lg3 phenotypes that correlate well with the level of ectopic Lg3 expression. High levels of ectopic LG3 mRNA expression results in a severe Lg3 phenotype, whereas weak ectopic Lg3 expression results in a mild Lg3 phenotype. We propose that ectopic Lg3 expression early in leaf development causes the blade-to-sheath transformation, but the level of expression determines the extent of the transformation.
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MESH Headings
- Alleles
- Amino Acid Sequence
- Base Sequence
- DNA Primers/genetics
- DNA, Complementary/genetics
- DNA, Plant/genetics
- Gene Expression Regulation, Developmental
- Gene Expression Regulation, Plant
- Genes, Homeobox
- Genes, Plant
- Genetic Linkage
- Homeodomain Proteins/genetics
- Molecular Sequence Data
- Mutation
- Plant Leaves/cytology
- Plant Leaves/enzymology
- Plant Leaves/growth & development
- Plant Proteins/genetics
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Plant/genetics
- RNA, Plant/metabolism
- Sequence Homology, Amino Acid
- Zea mays/cytology
- Zea mays/genetics
- Zea mays/growth & development
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Affiliation(s)
- G J Muehlbauer
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA.
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32
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Chan RL, Gago GM, Palena CM, Gonzalez DH. Homeoboxes in plant development. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1442:1-19. [PMID: 9767075 DOI: 10.1016/s0167-4781(98)00119-5] [Citation(s) in RCA: 153] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The homeobox is a 180 bp consensus DNA sequence present in a number of genes involved in developmental processes. This review focuses on the structure and function of plant homeobox genes and of the proteins they encode. Plant homeobox genes have been identified in studies using mutants, degenerate oligonucleotides deduced from conserved sequences, differential screening or binding to known promoters. According to sequence conservation, plant homeoboxes can be subdivided into different families, each comprising several members. Evolutionary studies indicate that the different families have diverged prior to the separation of the branches leading to animals, plants and fungi. Accordingly, members of different families show characteristic structural and functional properties. As an example, kn1-like genes seem to be involved in different aspects of the control of cell fate determination in the shoot meristem; HD-Zip genes, which encode proteins containing a leucine zipper motif adjacent to the homeodomain, are believed to operate at later stages of development; and gl2-like genes are involved in epidermal cell differentiation. Future studies should be oriented to discern the precise function of the many homeobox genes present in plant genomes, and to evaluate their use as modifiers of plant development.
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Affiliation(s)
- R L Chan
- Area Biología Molecular, Facultad de Ciencias Bioquímicas y Farmacéuticas (UNR) and Programa Multidisciplinario de Biología Experimental (PROMUBIE, CONICET), Suipacha 531, 2000 Rosario, Argentina
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33
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Abstract
Homeodomain-containing transcription factors play a variety of important roles in plant, animal, and fungal development. Mutational and evolutionary analysis is beginning to pinpoint specific roles of homeobox genes in plant meristem function. Even though many different plant homeobox genes encode very similar homeodomain sequences, overexpression studies suggest the existence of several levels of regulation that may specify the functions of the different proteins. Recent analysis of the maize Knotted1 gene and its orthologue in barley demonstrates some of these regulatory processes.
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Affiliation(s)
- R W Williams
- California Institute of Technology, Division of Biology, Pasadena 91125, USA.
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