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Xu P, Jinbo H, Cai W. Karrikin signaling regulates hypocotyl shade avoidance response by modulating auxin homeostasis in Arabidopsis. THE NEW PHYTOLOGIST 2022; 236:1748-1761. [PMID: 36068957 DOI: 10.1111/nph.18459] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 08/25/2022] [Indexed: 06/15/2023]
Abstract
Shade affects all aspects of plant growth and development, including seed germination, hypocotyl elongation, petiole growth, leaf hyponasty, and flowering time. Here, we found that mutations in the key Arabidopsis karrikins signal perception-associated KARRIKIN INSENSITIVE 2 (KAI2) gene, encoding an α/β-fold hydrolase, and the MORE AXILLARY GROWTH 2 (MAX2) gene, encoding an F-box protein, led to greater hypocotyl elongation under shade avoidance conditions. We further verified that these phenotypes were caused by perception of the endogenous KAI2-ligands (KLs), and that this phenotype is independent of strigolactone biosynthetic or signaling pathways. Upon perception of a KL, it is probable that the target protein forms a complex with the KAI2/MAX2 proteins, which are degraded through the action of the 26S proteasome. We demonstrated that SUPPRESSOR OF MAX2-1 (SMAX1) is the degradation target for the KAI2/MAX2 complex in the context of shade avoidance. KAI2 and MAX2 require SMAX1 to limit the hypocotyl growth associated with shade avoidance. Treatment with l-kynurenine, an inhibitor of auxin accumulation, partially restored elongation of kai2 mutant hypocotyls under simulated shade. Furthermore, KAI2 is involved in regulating auxin accumulation and polar auxin transport, which may contribute to the hypocotyl shade response. In addition, SMAX1 gene overexpression promoted the hypocotyl shade response. RNA-sequencing analysis revealed that SMAX1-overexpression affected the expression of many auxin homeostasis genes, especially under simulated shade. Altogether, our data support the conclusion that KL signaling regulates shade avoidance by modulating auxin homeostasis in the hypocotyl.
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Affiliation(s)
- Peipei Xu
- Laboratory of Photosynthesis and Environment, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Hu Jinbo
- Laboratory of Photosynthesis and Environment, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
- University of Chinese Academy of Sciences, Beijing, 100039, China
| | - Weiming Cai
- Laboratory of Photosynthesis and Environment, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
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Li Z, Pi Y, Zhai C, Xu D, Ma W, Chen H, Li Y, Wu H. The strigolactone receptor SlDWARF14 plays a role in photosynthetic pigment accumulation and photosynthesis in tomato. PLANT CELL REPORTS 2022; 41:2089-2105. [PMID: 35907035 DOI: 10.1007/s00299-022-02908-4] [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: 04/06/2022] [Accepted: 07/12/2022] [Indexed: 06/15/2023]
Abstract
Tomato DWARF14 regulates the development of roots, shoot branches and leaves, and also plays a role in photosynthetic pigment accumulation and photosynthetic capacity. Strigolactones (SLs) are a novel class of plant hormones. DWARF14 (D14) is the only SL receptor identified to date, but it is not functionally analyzed in tomato (Solanum lycopersicum). In the present study, we identified the potential SL receptor in tomato by bioinformatic analysis, which was designated as SlD14. SlD14 was expressed in roots, stems, flowers and developing fruits, with the highest expression level in leaves. sld14 mutant plants produced by the CRISPR/Cas9 system displayed reduced plant height and root biomass, increased shoot branching and altered leaf shape comparing with WT plants. The cytokinin biosynthetic gene ISOPENTENYLTRANSFERASE 3 (SlIPT3), auxin biosynthetic genes FLOOZY (SlFZY) and TRYPTOPHAN AMINOTRANSFERASE RELATED 1 (SlTAR1) and several auxin transport genes SlPINs, which are involved in branch formation, showed higher expression levels in the sld14 plant stem. In addition, sld14 plants exhibited light-green leaves, reduced chlorophyll and carotenoid contents, abnormal chloroplast structure and reduced photosynthetic capacity. Transcriptomic analysis showed that the transcript levels of six chlorophyll biosynthetic genes, three carotenoid biosynthetic genes and numerous chlorophyll a/b-binding protein genes were decreased in sld14 plants. These results suggest that tomato SL receptor gene SlD14 not only regulates the development of roots, shoot branches and leaves, but also plays a role in regulating photosynthetic pigment accumulation and photosynthetic capacity.
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Affiliation(s)
- Zhifei Li
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Ying Pi
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Changsheng Zhai
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Dong Xu
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Wenyao Ma
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Hong Chen
- Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, 210014, China
| | - Yi Li
- Department of Plant Science and Landscape Architecture, University of Connecticut, Storrs, CT, 06269, USA
| | - Han Wu
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
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Park YJ, Kim JY, Park CM. SMAX1 potentiates phytochrome B-mediated hypocotyl thermomorphogenesis. THE PLANT CELL 2022; 34:2671-2687. [PMID: 35478037 PMCID: PMC9252492 DOI: 10.1093/plcell/koac124] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 03/16/2022] [Indexed: 05/19/2023]
Abstract
Plant thermosensors help optimize plant development and architecture for ambient temperatures, and morphogenic adaptation to warm temperatures has been extensively studied in recent years. Phytochrome B (phyB)-mediated thermosensing and the gene regulatory networks governing thermomorphogenic responses are well understood at the molecular level. However, it is unknown how plants manage their responsiveness to fluctuating temperatures in inducing thermomorphogenic behaviors. Here, we demonstrate that SUPPRESSOR OF MAX2 1 (SMAX1), known as a karrikin signaling repressor, enhances the thermosensitivity of hypocotyl morphogenesis in Arabidopsis thaliana. Hypocotyl thermomorphogenesis was largely disrupted in SMAX1-deficient mutants. SMAX1 interacts with phyB to alleviate its suppressive effects on the transcription factor activity of PHYTOCHROME-INTERACTING FACTOR 4 (PIF4), promoting hypocotyl thermomorphogenesis. Interestingly, the SMAX1 protein is slowly destabilized at warm temperatures, preventing hypocotyl overgrowth. Our findings indicate that the thermodynamic control of SMAX1 abundance serves as a molecular gatekeeper for phyB function in thermosensitizing PIF4-mediated hypocotyl morphogenesis.
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Affiliation(s)
- Young-Joon Park
- Department of Chemistry, Seoul National University, Seoul 08826, Korea
| | - Jae Young Kim
- Department of Chemistry, Seoul National University, Seoul 08826, Korea
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Hamon‐Josse M, Villaécija‐Aguilar JA, Ljung K, Leyser O, Gutjahr C, Bennett T. KAI2 regulates seedling development by mediating light-induced remodelling of auxin transport. THE NEW PHYTOLOGIST 2022; 235:126-140. [PMID: 35313031 PMCID: PMC9320994 DOI: 10.1111/nph.18110] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 03/05/2022] [Indexed: 05/13/2023]
Abstract
Photomorphogenic remodelling of seedling growth is a key developmental transition in the plant life cycle. The α/β-hydrolase signalling protein KARRIKIN-INSENSITIVE2 (KAI2), a close homologue of the strigolactone receptor DWARF14 (D14), is involved in this process, but it is unclear how the effects of KAI2 on development are mediated. Here, using a combination of physiological, pharmacological, genetic and imaging approaches in Arabidopsis thaliana (Heynh.) we show that kai2 phenotypes arise because of a failure to downregulate auxin transport from the seedling shoot apex towards the root system, rather than a failure to respond to light per se. We demonstrate that KAI2 controls the light-induced remodelling of the PIN-mediated auxin transport system in seedlings, promoting a reduction in PIN7 abundance in older tissues, and an increase of PIN1/PIN2 abundance in the root meristem. We show that removing PIN3, PIN4 and PIN7 from kai2 mutants, or pharmacological inhibition of auxin transport and synthesis, is sufficient to suppress most kai2 seedling phenotypes. We conclude that KAI2 regulates seedling morphogenesis by its effects on the auxin transport system. We propose that KAI2 is not required for the light-mediated changes in PIN gene expression but is required for the appropriate changes in PIN protein abundance within cells.
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Affiliation(s)
- Maxime Hamon‐Josse
- School of BiologyFaculty of Biological SciencesUniversity of LeedsLeedsLS2 9JTUK
| | | | - Karin Ljung
- Department of Forest Genetics and Plant PhysiologyUmeå Plant Science CentreSwedish University of Agricultural SciencesSE‐901 83UmeåSweden
| | - Ottoline Leyser
- Sainsbury Laboratory Cambridge UniversityBateman StreetCambridgeCB2 1LRUK
| | - Caroline Gutjahr
- Plant GeneticsTUM School of Life SciencesTechnical University of Munich (TUM)Emil Ramann Str. 485354FreisingGermany
- GeneticsFaculty of BiologyLMU MunichGrosshaderner St. 482152MartinsriedGermany
| | - Tom Bennett
- School of BiologyFaculty of Biological SciencesUniversity of LeedsLeedsLS2 9JTUK
- Sainsbury Laboratory Cambridge UniversityBateman StreetCambridgeCB2 1LRUK
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Bursch K, Niemann ET, Nelson DC, Johansson H. Karrikins control seedling photomorphogenesis and anthocyanin biosynthesis through a HY5-BBX transcriptional module. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 107:1346-1362. [PMID: 34160854 DOI: 10.1111/tpj.15383] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 06/18/2021] [Indexed: 05/15/2023]
Abstract
The butenolide molecule, karrikin (KAR), emerging in smoke of burned plant material, enhances light responses such as germination, inhibition of hypocotyl elongation, and anthocyanin accumulation in Arabidopsis. The KAR signaling pathway consists of KARRIKIN INSENSITIVE 2 (KAI2) and MORE AXILLARY GROWTH 2 (MAX2), which, upon activation, act in an SCF E3 ubiquitin ligase complex to target the downstream signaling components SUPPRESSOR OF MAX2 1 (SMAX1) and SMAX1-LIKE 2 (SMXL2) for degradation. How degradation of SMAX1 and SMXL2 is translated into growth responses remains unknown. Although light clearly influences the activity of KAR, the molecular connection between the two pathways is still poorly understood. Here, we demonstrate that the KAR signaling pathway promotes the activity of a transcriptional module consisting of ELONGATED HYPOCOTYL 5 (HY5), B-BOX DOMAIN PROTEIN 20 (BBX20), and BBX21. The bbx20 bbx21 mutant is largely insensitive to treatment with KAR2 , similar to a hy5 mutant, with regards to inhibition of hypocotyl elongation and anthocyanin accumulation. Detailed analysis of higher order mutants in combination with RNA-sequencing analysis revealed that anthocyanin accumulation downstream of SMAX1 and SMXL2 is fully dependent on the HY5-BBX module. However, the promotion of hypocotyl elongation by SMAX1 and SMXL2 is, in contrast to KAR2 treatment, only partially dependent on BBX20, BBX21, and HY5. Taken together, these results suggest that light- and KAR-dependent signaling intersect at the HY5-BBX transcriptional module.
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Affiliation(s)
- Katharina Bursch
- Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences (DCPS), Freie Universität Berlin, Berlin, 14195, Germany
| | - Ella T Niemann
- Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences (DCPS), Freie Universität Berlin, Berlin, 14195, Germany
| | - David C Nelson
- Department of Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA
| | - Henrik Johansson
- Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences (DCPS), Freie Universität Berlin, Berlin, 14195, Germany
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