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Yu KMJ, Oliver J, McKinley B, Weers B, Fabich HT, Evetts N, Conradi MS, Altobelli SA, Marshall-Colon A, Mullet J. Bioenergy sorghum stem growth regulation: intercalary meristem localization, development, and gene regulatory network analysis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 112:476-492. [PMID: 36038985 DOI: 10.1111/tpj.15960] [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: 04/22/2022] [Revised: 08/18/2022] [Accepted: 08/20/2022] [Indexed: 06/15/2023]
Abstract
Bioenergy sorghum is a highly productive drought tolerant C4 grass that accumulates 80% of its harvestable biomass in approximately 4 m length stems. Stem internode growth is regulated by development, shading, and hormones that modulate cell proliferation in intercalary meristems (IMs). In this study, sorghum stem IMs were localized above the pulvinus at the base of elongating internodes using magnetic resonance imaging, microscopy, and transcriptome analysis. A change in cell morphology/organization occurred at the junction between the pulvinus and internode where LATERAL ORGAN BOUNDARIES (SbLOB), a boundary layer gene, was expressed. Inactivation of an AGCVIII kinase in DDYM (dw2) resulted in decreased SbLOB expression, disrupted IM localization, and reduced internode cell proliferation. Transcriptome analysis identified approximately 1000 genes involved in cell proliferation, hormone signaling, and other functions selectively upregulated in the IM compared with a non-meristematic stem tissue. This cohort of genes is expressed in apical dome stem tissues before localization of the IM at the base of elongating internodes. Gene regulatory network analysis identified connections between genes involved in hormone signaling and cell proliferation. The results indicate that gibberellic acid induces accumulation of growth regulatory factors (GRFs) known to interact with ANGUSTIFOLIA (SbAN3), a master regulator of cell proliferation. GRF:AN3 was predicted to induce SbARF3/ETT expression and regulate SbAN3 expression in an auxin-dependent manner. GRFs and ARFs regulate genes involved in cytokinin and brassinosteroid signaling and cell proliferation. The results provide a molecular framework for understanding how hormone signaling regulates the expression of genes involved in cell proliferation in the stem IM.
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Affiliation(s)
- Ka Man Jasmine Yu
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, 77843-2128, USA
| | - Joel Oliver
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, 77843-2128, USA
| | - Brian McKinley
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, 77843-2128, USA
| | - Brock Weers
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, 77843-2128, USA
| | - Hilary T Fabich
- ABQMR, Inc., 2301 Yale Blvd. SE, Suite C2, Albuquerque, New Mexico, 87106, USA
| | - Nathan Evetts
- ABQMR, Inc., 2301 Yale Blvd. SE, Suite C2, Albuquerque, New Mexico, 87106, USA
| | - Mark S Conradi
- ABQMR, Inc., 2301 Yale Blvd. SE, Suite C2, Albuquerque, New Mexico, 87106, USA
| | - Stephen A Altobelli
- ABQMR, Inc., 2301 Yale Blvd. SE, Suite C2, Albuquerque, New Mexico, 87106, USA
| | - Amy Marshall-Colon
- Department of Plant Biology, University of Illinois, Champaign-Urbana, Illinois, 61801, USA
| | - John Mullet
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, 77843-2128, USA
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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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Machida Y, Suzuki T, Sasabe M, Iwakawa H, Kojima S, Machida C. Arabidopsis ASYMMETRIC LEAVES2 (AS2): roles in plant morphogenesis, cell division, and pathogenesis. JOURNAL OF PLANT RESEARCH 2022; 135:3-14. [PMID: 34668105 PMCID: PMC8755679 DOI: 10.1007/s10265-021-01349-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Accepted: 09/21/2021] [Indexed: 05/26/2023]
Abstract
The ASYMMETRIC LEAVES2 (AS2) gene in Arabidopsis thaliana is responsible for the development of flat, symmetric, and extended leaf laminae and their vein systems. AS2 protein is a member of the plant-specific AS2/LOB protein family, which includes 42 members comprising the conserved amino-terminal domain referred to as the AS2/LOB domain, and the variable carboxyl-terminal region. Among the members, AS2 has been most intensively investigated on both genetic and molecular levels. AS2 forms a complex with the myb protein AS1, and is involved in epigenetic repression of the abaxial genes ETTIN/AUXIN RESPONSE FACTOR3 (ETT/ARF3), ARF4, and class 1 KNOX homeobox genes. The repressed expression of these genes by AS2 is markedly enhanced by the cooperative action of various modifier genes, some of which encode nucleolar proteins. Further downstream, progression of the cell division cycle in the developing organs is stimulated; meristematic states are suppressed in determinate leaf primordia; and the extension of leaf primordia is induced. AS2 binds the specific sequence in exon 1 of ETT/ARF3 and maintains methylated CpGs in several exons of ETT/ARF3. AS2 forms bodies (designated as AS2 bodies) at nucleolar peripheries. AS2 bodies partially overlap chromocenters, including inactive 45S ribosomal DNA repeats, suggesting the presence of molecular and functional links among AS2, the 45S rDNAs, and the nucleolus to exert the repressive regulation of ETT/ARF3. The AS2/LOB domain is characterized by three subdomains, the zinc finger (ZF) motif, the internally conserved-glycine containing (ICG) region, and the leucine-zipper-like (LZL) region. Each of these subdomains is essential for the formation of AS2 bodies. ICG to LZL are required for nuclear localization, but ZF is not. LZL intrinsically has the potential to be exported to the cytoplasm. In addition to its nuclear function, it has been reported that AS2 plays a positive role in geminivirus infection: its protein BV1 stimulates the expression of AS2 and recruits AS2 to the cytoplasm, which enhances virus infectivity by suppression of cytoplasmic post transcriptional gene silencing.
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Affiliation(s)
- Yasunori Machida
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi, 464-8602, Japan.
| | - Takanori Suzuki
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi, 464-8602, Japan
- Central Research Institute, Ishihara Sangyo Kaisha, Ltd., 2-3-1 Nishi-Shibukawa, Kusatsu, Shiga, 525-0025, Japan
| | - Michiko Sasabe
- Department of Biology, Faculty of Agriculture and Life Science, Hirosaki University, 3 Bunkyo-cho, Hirosaki, 036-8561, Japan
| | - Hidekazu Iwakawa
- Graduate School of Bioscience and Biotechnology, Chubu University, Kasugai, Aichi, 487-8501, Japan
| | - Shoko Kojima
- Graduate School of Bioscience and Biotechnology, Chubu University, Kasugai, Aichi, 487-8501, Japan
| | - Chiyoko Machida
- Graduate School of Bioscience and Biotechnology, Chubu University, Kasugai, Aichi, 487-8501, Japan
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Manuela D, Xu M. Patterning a Leaf by Establishing Polarities. FRONTIERS IN PLANT SCIENCE 2020; 11:568730. [PMID: 33193497 PMCID: PMC7661387 DOI: 10.3389/fpls.2020.568730] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 09/30/2020] [Indexed: 05/14/2023]
Abstract
Leaves are the major organ for photosynthesis in most land plants, and leaf structure is optimized for the maximum capture of sunlight and gas exchange. Three polarity axes, the adaxial-abaxial axis, the proximal-distal axis, and the medial-lateral axis are established during leaf development to give rise to a flattened lamina with a large area for photosynthesis and blades that are extended on petioles for maximum sunlight. Adaxial cells are elongated, tightly packed cells with many chloroplasts, and their fate is specified by HD-ZIP III and related factors. Abaxial cells are rounder and loosely packed cells and their fate is established and maintained by YABBY family and KANADI family proteins. The activities of adaxial and abaxial regulators are coordinated by ASYMMETRIC LEAVES2 and auxin. Establishment of the proximodistal axis involves the BTB/POZ domain proteins BLADE-ON-PETIOLE1 and 2, whereas homeobox genes PRESSED FLOWER and WUSCHEL-RELATED HOMEOBOX1 mediate leaf development along the mediolateral axis. This review summarizes recent advances in leaf polarity establishment with a focus on the regulatory networks involved.
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Affiliation(s)
| | - Mingli Xu
- Department of Biological Sciences, University of South Carolina, Columbia, SC, United States
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Iwakawa H, Takahashi H, Machida Y, Machida C. Roles of ASYMMETRIC LEAVES2 (AS2) and Nucleolar Proteins in the Adaxial-Abaxial Polarity Specification at the Perinucleolar Region in Arabidopsis. Int J Mol Sci 2020; 21:E7314. [PMID: 33022996 PMCID: PMC7582388 DOI: 10.3390/ijms21197314] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 09/27/2020] [Accepted: 09/29/2020] [Indexed: 12/14/2022] Open
Abstract
Leaves of Arabidopsis develop from a shoot apical meristem grow along three (proximal-distal, adaxial-abaxial, and medial-lateral) axes and form a flat symmetric architecture. ASYMMETRIC LEAVES2 (AS2), a key regulator for leaf adaxial-abaxial partitioning, encodes a plant-specific nuclear protein and directly represses the abaxial-determining gene ETTIN/AUXIN RESPONSE FACTOR3 (ETT/ARF3). How AS2 could act as a critical regulator, however, has yet to be demonstrated, although it might play an epigenetic role. Here, we summarize the current understandings of the genetic, molecular, and cellular functions of AS2. A characteristic genetic feature of AS2 is the presence of a number of (about 60) modifier genes, mutations of which enhance the leaf abnormalities of as2. Although genes for proteins that are involved in diverse cellular processes are known as modifiers, it has recently become clear that many modifier proteins, such as NUCLEOLIN1 (NUC1) and RNA HELICASE10 (RH10), are localized in the nucleolus. Some modifiers including ribosomal proteins are also members of the small subunit processome (SSUP). In addition, AS2 forms perinucleolar bodies partially colocalizing with chromocenters that include the condensed inactive 45S ribosomal RNA genes. AS2 participates in maintaining CpG methylation in specific exons of ETT/ARF3. NUC1 and RH10 genes are also involved in maintaining the CpG methylation levels and repressing ETT/ARF3 transcript levels. AS2 and nucleolus-localizing modifiers might cooperatively repress ETT/ARF3 to develop symmetric flat leaves. These results raise the possibility of a nucleolus-related epigenetic repression system operating for developmental genes unique to plants and predict that AS2 could be a molecule with novel functions that cannot be explained by the conventional concept of transcription factors.
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Affiliation(s)
- Hidekazu Iwakawa
- Graduate School of Bioscience and Biotechnology, Chubu University, 1200, Matsumoto-cho, Kasugai, Aichi 487-8501, Japan;
| | - Hiro Takahashi
- Graduate School of Medical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan;
| | - Yasunori Machida
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
| | - Chiyoko Machida
- Graduate School of Bioscience and Biotechnology, Chubu University, 1200, Matsumoto-cho, Kasugai, Aichi 487-8501, Japan;
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Ali S, Khan N, Xie L. Molecular and Hormonal Regulation of Leaf Morphogenesis in Arabidopsis. Int J Mol Sci 2020; 21:ijms21145132. [PMID: 32698541 PMCID: PMC7404056 DOI: 10.3390/ijms21145132] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 07/14/2020] [Accepted: 07/15/2020] [Indexed: 12/28/2022] Open
Abstract
Shoot apical meristems (SAM) are tissues that function as a site of continuous organogenesis, which indicates that a small pool of pluripotent stem cells replenishes into lateral organs. The coordination of intercellular and intracellular networks is essential for maintaining SAM structure and size and also leads to patterning and formation of lateral organs. Leaves initiate from the flanks of SAM and then develop into a flattened structure with variable sizes and forms. This process is mainly regulated by the transcriptional regulators and mechanical properties that modulate leaf development. Leaf initiation along with proper orientation is necessary for photosynthesis and thus vital for plant survival. Leaf development is controlled by different components such as hormones, transcription factors, miRNAs, small peptides, and epigenetic marks. Moreover, the adaxial/abaxial cell fate, lamina growth, and shape of margins are determined by certain regulatory mechanisms. The over-expression and repression of various factors responsible for leaf initiation, development, and shape have been previously studied in several mutants. However, in this review, we collectively discuss how these factors modulate leaf development in the context of leaf initiation, polarity establishment, leaf flattening and shape.
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Affiliation(s)
- Shahid Ali
- College of Life Sciences, Northeast Forestry University, Harbin 150040, China
- Correspondence: (S.A.); (L.X.)
| | - Naeem Khan
- Department of Agronomy, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, USA;
| | - Linan Xie
- College of Life Sciences, Northeast Forestry University, Harbin 150040, China
- Key Laboratory of Saline-Alkali Vegetative Ecology Restoration, Ministry of Education, College of Life Science, Northeast Forestry University, Harbin 150040, China
- Correspondence: (S.A.); (L.X.)
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