1
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Kępczyński J, Dziurka M, Wójcik A. KAR 1-induced dormancy release in Avena fatua caryopses involves reduction of caryopsis sensitivity to ABA and ABA/GA s ratio in coleorhiza and radicle. PLANTA 2024; 259:126. [PMID: 38635035 PMCID: PMC11026216 DOI: 10.1007/s00425-024-04387-1] [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: 02/16/2024] [Accepted: 03/10/2024] [Indexed: 04/19/2024]
Abstract
MAIN CONCLUSION The dormancy release by KAR1 is associated with a reduction of coleorhiza and radicle sensitivity to ABA as well as with reduction the ABA/GAs ratio in the coleorhiza, by a decrease content of ABA, and in the radicle, by a decrease the ABA and an increase of the GAs contents. Both, karrikin 1 (KAR1) and gibberellin A3 (GA3), release dormancy in Avena fatua caryopses, resulting in the emergence of coleorhiza (CE) and radicle (RE). Moreover, KAR1 and GA3 stimulate CE and RE in the presence of abscisic acid (ABA), the stimulation being more effective in CE. The stimulatory effects of KAR1 and GA3 involve also the CE and RE rates. A similar effect was observed at KAR1 concentrations much lower than those of GA3. KAR1 increased the levels of bioactive GA5 and GA6 in embryos and the levels of GA1, GA5, GA3, GA6 and GA4 in radicles. The stimulatory effect of KAR1 on germination, associated with increased levels of gibberellins (GAs) and reduced levels of ABA in embryos, was counteracted by paclobutrazol (PAC), commonly regarded as a GAs biosynthesis inhibitor. Consequently, KAR1 decreased the ABA/GAs ratio, whereas PAC, used alone or in combination with KAR1, increased it. The ABA/GAs ratio was reduced by KAR1 in both coleorhiza and radicle, the effect being stronger in the latter. We present the first evidence that KAR1-induced dormancy release requires a decreased ABA/GAs ratio in coleorhiza and radicle. It is concluded that the dormancy-releasing effect of KAR1 in A. fatua caryopses includes (i) a reduction of the coleorhiza and radicle sensitivity to ABA, and (2) a reduction of the ABA/GAs ratio (i) in the coleorhiza, by decreasing the ABA content, and (ii) in the radicle, by decreasing the ABA and increasing the content GAs, particularly GA1. The results may suggest different mechanisms of dormancy release by KAR1 in monocot and dicot seeds.
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Affiliation(s)
- Jan Kępczyński
- Institute of Biology, University of Szczecin, Waska 13, 71-415, Szczecin, Poland.
| | - Michal Dziurka
- Institute of Plant Physiology, Polish Academy of Sciences, Niezapominajek 21, 20-239, Krakow, Poland
| | - Agata Wójcik
- Institute of Biology, University of Szczecin, Waska 13, 71-415, Szczecin, Poland
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2
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Kępczyński J, Wójcik A, Dziurka M. NO-mediated dormancy release of Avena fatua caryopses is associated with decrease in abscisic acid sensitivity, content and ABA/GA s ratios. PLANTA 2023; 257:101. [PMID: 37087501 PMCID: PMC10122620 DOI: 10.1007/s00425-023-04117-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Accepted: 03/07/2023] [Indexed: 05/03/2023]
Abstract
MAIN CONCLUSION NO releases caryopsis dormancy in Avena fatua, the effect being dependent on the level of dormancy. The NO effect involves also the reduction of caryopsis sensitivity to ABA and to a decrease in the ABA to GAs ratio due to a decrease in ABA levels and the lack of effect on GAs levels before germination is completed. Nitric oxide (NO) from various donors (i.e. SNP, GSNO and acidified KNO2), applied to dry caryopses or during initial germination, released primary dormancy in caryopses. Dormancy in caryopses was gradually lost during dry storage (after-ripening) at 25 °C, enabling germination at 20 °C in the dark. The after-ripening effect is associated with a decrease in NO required for germination. In addition, NO decreased the sensitivity of dormant caryopses to exogenous abscisic acid (ABA) and decreased the embryos' ABA content before germination was completed. However, NO did not affect the content of bioactive gibberellins (GAs) from non-13-hydroxylation (GA4, GA7) and 13-hydroxylation (GA1, GA3, GA6.) pathways. Paclobutrazol (PAC), commonly regarded as a GAs biosynthesis inhibitor, counteracted the dormancy-releasing effect of NO and did not affect the GAs level; however, it increased the ABA content in embryos before germination was completed. Ascorbic acid, sodium benzoate and tiron, scavengers of reactive oxygen species (ROS), reduced the stimulatory effect of NO on caryopsis germination. This work provides new insight on the participation of NO in releasing A. fatua caryopses dormancy and on the relationship of NO with endogenous ABA and GAs.
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Affiliation(s)
- Jan Kępczyński
- Institute of Biology, University of Szczecin, Wąska 13, 71-415, Szczecin, Poland.
| | - Agata Wójcik
- Institute of Biology, University of Szczecin, Wąska 13, 71-415, Szczecin, Poland
| | - Michał Dziurka
- Institute of Plant Physiology, Polish Academy of Sciences, Niezapominajek 21, 20-239, Krakow, Poland
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3
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Naing AH, Campol JR, Jeong HY, Chung MY, Kim WC, Kim CK. Overexpression of acdS gene encoding 1-aminocyclopropane-1-carboxylic acid deaminase enzyme in petunia negatively affects seed germination. PLANT CELL REPORTS 2022; 41:2201-2211. [PMID: 35988098 DOI: 10.1007/s00299-022-02916-4] [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: 03/16/2022] [Accepted: 08/01/2022] [Indexed: 06/15/2023]
Abstract
Overexpression of acdS in petunia negatively affects seed germination by suppression of ethylene biosynthesis and signaling genes and induction of abscisic acid biosynthesis genes in the seeds. The acdS gene, which encodes 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, has been overexpressed in horticultural crops to improve their tolerance to abiotic stress. However, the role of acdS in the germination of crop seeds has not been investigated, despite its suppression of ethylene production. In this study, acdS overexpression significantly reduced seed weight and germination rate in transgenic petunia cv. Merage Rose (T5, T7, and T12) relative to wild type via the suppression of ethylene biosynthesis and signaling genes and induction of abscisic acid (ABA) biosynthesis genes. The germination rate of T7 was significantly lower than those of T5 and T12, which was linked to higher expression of acdS in the former than the latter. The addition of exogenous ACC and gibberellic acid (GA3) to the germination medium improved the germination rate of T5 seeds and GA3 promoted the germination rate of T12 seeds. However, neither ACC nor GA3 promoted the germination rate of T7 seeds. The improved germination rates in T5 and T12 were associated with the transcriptional regulation of ethylene biosynthesis genes, particularly that of the ACO1 gene, signaling genes, and ABA biosynthesis genes. In this study, we discovered a negative role of acdS in seed germination in petunia. Thus, we highlight the need to consider the negative effect of acdS on seed germination when overexpressing the gene in horticultural crops to improve tolerance to abiotic stress.
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Affiliation(s)
- Aung Htay Naing
- Department of Horticultural Science, Kyungpook National University, Daegu, South Korea
| | - Jova Riza Campol
- Department of Horticultural Science, Kyungpook National University, Daegu, South Korea
| | - Hui Yeong Jeong
- Department of Horticultural Science, Kyungpook National University, Daegu, South Korea
- Forest Medicinal Resources Research Center, NIFoS, Yeongju, South Korea
| | - Mi Young Chung
- Department of Agricultural Education, Sunchon National University, Suncheon, South Korea
| | - Won-Chan Kim
- School of Applied Biosciences, Kyungpook National University, Daegu, South Korea
| | - Chang Kil Kim
- Department of Horticultural Science, Kyungpook National University, Daegu, South Korea.
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4
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Naing AH, Xu J, Kim CK. Editing of 1-aminocyclopropane-1-carboxylate oxidase genes negatively affects petunia seed germination. PLANT CELL REPORTS 2022; 41:209-220. [PMID: 34665313 DOI: 10.1007/s00299-021-02802-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 10/11/2021] [Indexed: 06/13/2023]
Abstract
Editing of ACO genes involved in ethylene biosynthesis pathway reduces ethylene production in petunia seeds and inhibits seed germination. Ethylene production in the seeds of Petunia hybrida cv. 'Mirage Rose' was associated with expression of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO) genes (PhACO1, PhACO3, and PhACO4). Suppression of their expression by ethylene inhibitor silver thiosulphate (STS) significantly reduced ethylene production and inhibited seed germination. When it was combined with ethylene precursor ACC, ethylene production was re-promoted via activation of the genes and higher seed germination was restored. This was confirmed using the mutants editing the genes and WT. In the present study, compared with wild type plants, three different mutants (phaco1, phaco3, and phaco4) showed significantly decreased germination percentages as well as delayed germination time and seedling growth. These reductions were associated with lighter seed weight, lower ACO transcript levels, and lower ethylene production in mutants. Inhibited seed germination owing to reduced ethylene production was further verified by the supplementation of exogenous ACC and gibberellic acid (GA3) to growth medium, which restored high seed germination activity in all mutants via enhanced ethylene production. In this study, we reported a key regulatory role of ethylene in seed germination mechanisms in petunia. Further, we highlighted on need to consider the negative effects of ethylene reduction in seed germination and plant growth when editing genes in the ethylene biosynthesis pathway for the maintenance of postharvest fruit, vegetable, and flower quality.
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Affiliation(s)
- Aung Htay Naing
- Department of Horticulture, Kyungpook National University, Daegu, 41566, Korea
| | - Junping Xu
- Department of Horticulture, Kyungpook National University, Daegu, 41566, Korea
- Floriculture Research Division, Rural Development Administration, National Institute of Horticultural and Herbal Science, Wanju, 55365, Korea
| | - Chang Kil Kim
- Department of Horticulture, Kyungpook National University, Daegu, 41566, Korea.
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Holloway T, Steinbrecher T, Pérez M, Seville A, Stock D, Nakabayashi K, Leubner-Metzger G. Coleorhiza-enforced seed dormancy: a novel mechanism to control germination in grasses. THE NEW PHYTOLOGIST 2021; 229:2179-2191. [PMID: 32970853 DOI: 10.1111/nph.16948] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 09/04/2020] [Indexed: 05/07/2023]
Abstract
How the biophysical properties of overlaying tissues control growth, such as the embryonic root (radicle) during seed germination, is a fundamental question. In eudicot seeds the endosperm surrounding the radicle confers coat dormancy and controls germination responses through modulation of its cell wall mechanical properties. Far less is known for grass caryopses that differ in tissue morphology. Here we report that the coleorhiza, a sheath-like organ that surrounds the radicle in grass embryos, performs the same role in the grass weed Avena fatua (common wild oat). We combined innovative biomechanical techniques, tissue ablation, microscopy, tissue-specific gene and enzyme activity expression with the analysis of hormones and oligosaccharides. The combined experimental work demonstrates that in grass caryopses the coleorhiza indeed controls germination for which we provide direct biomechanical evidence. We show that the coleorhiza becomes reinforced during dormancy maintenance and weakened during germination. Xyloglucan endotransglycosylases/hydrolases may have a role in coleorhiza reinforcement through cell wall remodelling to confer coat dormancy. The control of germination by coleorhiza-enforced dormancy in grasses is an example of the convergent evolution of mechanical restraint by overlaying tissues.
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Affiliation(s)
- Thomas Holloway
- Department of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
- Syngenta, Jealott's Hill International Research Centre, Warfield, Bracknell,, RG42 6EY, UK
| | - Tina Steinbrecher
- Department of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
| | - Marta Pérez
- Department of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
| | - Anne Seville
- Syngenta, Jealott's Hill International Research Centre, Warfield, Bracknell,, RG42 6EY, UK
| | - David Stock
- Syngenta, Jealott's Hill International Research Centre, Warfield, Bracknell,, RG42 6EY, UK
| | - Kazumi Nakabayashi
- Department of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
| | - Gerhard Leubner-Metzger
- Department of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
- Laboratory of Growth Regulators, Palacký University and Institute of Experimental Botany, Czech Academy of Sciences, Olomouc, CZ-78371, Czech Republic
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6
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Kępczyński J, Wójcik A, Dziurka M. Avena fatua caryopsis dormancy release is associated with changes in KAR 1 and ABA sensitivity as well as with ABA reduction in coleorhiza and radicle. PLANTA 2021; 253:52. [PMID: 33507406 PMCID: PMC7843558 DOI: 10.1007/s00425-020-03562-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 12/31/2020] [Indexed: 05/07/2023]
Abstract
The dormancy release in Avena fatua caryopses was associated with a reduction in the ABA content in embryos, coleorhiza and radicle. The coleorhiza proved more sensitive to KAR1 and less sensitive to ABA than the radicle. The inability of dormant caryopses and ABA-treated non-dormant caryopses to complete germination is related to inhibition and delayed of cell-cycle activation, respectively. As freshly harvested Avena fatua caryopses are dormant at 20 °C, they cannot complete germination; the radicle is not able to emerge. Both karrikin 1 (KAR1) and dry after-ripening release dormancy, enabling the emergence of, first, the coleorhiza and later the radicle. The after-ripening removes caryopse sensitivity to KAR1 and decreases the sensitivity to abscisic acid (ABA). The coleorhiza was found to be more sensitive to KAR1, and less sensitive to ABA, than radicles. Effects of KAR1 and after-ripening were associated with a reduction of the embryo's ABA content during caryopsis germination. KAR1 was found to decrease the ABA content in the coleorhiza and radicles. Germination of after-ripened caryopses was associated with the progress of cell-cycle activation before coleorhiza emergence. Inhibition of the germination completion due to dormancy or treating the non-dormant caryopses with ABA was associated with a total and partial inhibition of cell-cycle activation, respectively.
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Affiliation(s)
- Jan Kępczyński
- Institute of Biology, University of Szczecin, Wąska 13, 71-415, Szczecin, Poland.
| | - Agata Wójcik
- Institute of Biology, University of Szczecin, Wąska 13, 71-415, Szczecin, Poland
| | - Michał Dziurka
- Institute of Plant Physiology, Polish Academy of Sciences, Niezapominajek 21, 20-239, Krakow, Poland
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7
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Kępczyński J, Wójcik A, Dziurka M. Avena fatua caryopsis dormancy release is associated with changes in KAR 1 and ABA sensitivity as well as with ABA reduction in coleorhiza and radicle. PLANTA 2021; 253:52. [PMID: 33507406 DOI: 10.1007/s00425-020-03562-3564] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 12/31/2020] [Indexed: 05/25/2023]
Abstract
The dormancy release in Avena fatua caryopses was associated with a reduction in the ABA content in embryos, coleorhiza and radicle. The coleorhiza proved more sensitive to KAR1 and less sensitive to ABA than the radicle. The inability of dormant caryopses and ABA-treated non-dormant caryopses to complete germination is related to inhibition and delayed of cell-cycle activation, respectively. As freshly harvested Avena fatua caryopses are dormant at 20 °C, they cannot complete germination; the radicle is not able to emerge. Both karrikin 1 (KAR1) and dry after-ripening release dormancy, enabling the emergence of, first, the coleorhiza and later the radicle. The after-ripening removes caryopse sensitivity to KAR1 and decreases the sensitivity to abscisic acid (ABA). The coleorhiza was found to be more sensitive to KAR1, and less sensitive to ABA, than radicles. Effects of KAR1 and after-ripening were associated with a reduction of the embryo's ABA content during caryopsis germination. KAR1 was found to decrease the ABA content in the coleorhiza and radicles. Germination of after-ripened caryopses was associated with the progress of cell-cycle activation before coleorhiza emergence. Inhibition of the germination completion due to dormancy or treating the non-dormant caryopses with ABA was associated with a total and partial inhibition of cell-cycle activation, respectively.
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Affiliation(s)
- Jan Kępczyński
- Institute of Biology, University of Szczecin, Wąska 13, 71-415, Szczecin, Poland.
| | - Agata Wójcik
- Institute of Biology, University of Szczecin, Wąska 13, 71-415, Szczecin, Poland
| | - Michał Dziurka
- Institute of Plant Physiology, Polish Academy of Sciences, Niezapominajek 21, 20-239, Krakow, Poland
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8
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Oliveira MC, Osipitan OA, Begcy K, Werle R. Cover crops, hormones and herbicides: Priming an integrated weed management strategy. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2020; 301:110550. [PMID: 33218616 DOI: 10.1016/j.plantsci.2020.110550] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 05/25/2020] [Accepted: 06/04/2020] [Indexed: 06/11/2023]
Abstract
Herbicide weed resistance has been a major issue of conventional global row crop agriculture for decades. Still current strategies and novel technologies available to address weed resistance are mainly herbicide-based. Thus, there is a need for innovative means of integrated weed management strategies. Our approach proposed herein integrates cover crops, plant hormones and pre-emergence (PRE) herbicides as part of weed management programs. Plant hormones such as gibberellic acid (GA3) and abscisic acid (ABA) have the potential to induce seed germination and seed dormancy, respectively. Prior to crop emergence, plant hormones are tank mixed with PRE herbicides and sprayed to cover crop residue. Two strategies are proposed (1) PRE herbicides + GA3 and (2) PRE herbicide + ABA. The hormones provide different results; GA3 is likely to stimulate a more uniform weed seed germination, thus enhancing efficacy of PRE herbicides. Conversely, ABA could promote weed seed dormancy, reducing selection pressure and weed infestations until crop canopy closure. Much research is needed to understand the impact of hormones on weed and crop species, optimize products and rates, and compatibility of hormones with herbicides and cover crops. If successful, this approach could open a new opportunity for agricultural business, enhance farming sustainability by reducing dependence on herbicides and minimizing agronomic, economic and environmental issues related to weed resistance.
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Affiliation(s)
- Maxwel C Oliveira
- Department of Agronomy, Western São Paulo University, Presidente Prudente, São Paulo, 19067, Brazil; Department of Agronomy, University of Wisconsin-Madison, Madison, WI 53706, United States.
| | - O Adewale Osipitan
- Department of Plant Sciences, University of California-Davis, Davis, CA, 95616, United States.
| | - Kevin Begcy
- Environmental Horticulture Department, University of Florida, Gainesville, FL 32611, United States.
| | - Rodrigo Werle
- Department of Agronomy, University of Wisconsin-Madison, Madison, WI 53706, United States.
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9
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Liu S, Mi X, Zhang R, An Y, Zhou Q, Yang T, Xia X, Guo R, Wang X, Wei C. Integrated analysis of miRNAs and their targets reveals that miR319c/TCP2 regulates apical bud burst in tea plant (Camellia sinensis). PLANTA 2019; 250:1111-1129. [PMID: 31172343 DOI: 10.1007/s00425-019-03207-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 06/01/2019] [Indexed: 05/18/2023]
Abstract
MAIN CONCLUSION The roles of microRNA-mediated epigenetic regulation were highlighted in the bud dormancy-activity cycle, implying that certain differentially expressed miRNAs play crucial roles in apical bud burst, such as csn-miR319c/TCP2. microRNAs (miRNAs) are a class of small non-coding RNAs that regulate gene expression by targeting mRNA transcripts for cleavage or directing translational inhibition. To investigate whether miRNAs regulate bud dormancy-activation transition in tea plant, which largely affects the yield and price of tea products and adaptability of tea trees, we constructed small RNA libraries from three different periods of bud dormancy-burst transition. Through sequencing analysis, 262 conserved and 83 novel miRNAs were identified, including 118 differentially expressed miRNAs. Quantitative RT-PCR results for randomly selected miRNAs exhibited that our comprehensive analysis is highly reliable and accurate. The content of caffeine increased continuously from the endodormancy bud to flushing bud, and differentially expressed miRNAs coupling with their targets associated with bud burst were identified. Remarkably, csn-miR319c was downregulated significantly from the quiescent bud to burst bud, while its target gene CsnTCP2 (TEOSINTE BRANCHED/CYCLOIDEA/PROLIFERATING CELL FACTOR 2) displayed opposite expression patterns. Co-transformation experiment in tobacco demonstrated that csn-miR319c can significantly suppress the functions of CsnTCP2. This study on miRNAs and the recognition of target genes could provide new insights into the molecular mechanism of the bud dormancy-activation transition in tea plant.
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Affiliation(s)
- Shengrui Liu
- State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, 130 Changjiang West Road, Hefei, 230036, China
| | - Xiaozeng Mi
- State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, 130 Changjiang West Road, Hefei, 230036, China
| | - Ran Zhang
- Tea Research Institution, Anhui Academy of Agricultural Sciences, Huangshang, China
| | - Yanlin An
- State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, 130 Changjiang West Road, Hefei, 230036, China
| | - Qiying Zhou
- Henan Key Laboratory of Tea Plant Biology, Xinyang Normal University, 237 Nanhu Road, Xinyang, 464000, China
| | - Tianyuan Yang
- State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, 130 Changjiang West Road, Hefei, 230036, China
| | - Xiaobo Xia
- State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, 130 Changjiang West Road, Hefei, 230036, China
| | - Rui Guo
- State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, 130 Changjiang West Road, Hefei, 230036, China
| | - Xuewen Wang
- Department of Genetics, University of Georgia, Athens, GA, 30602, USA
| | - Chaoling Wei
- State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, 130 Changjiang West Road, Hefei, 230036, China.
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10
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Villaécija-Aguilar JA, Hamon-Josse M, Carbonnel S, Kretschmar A, Schmidt C, Dawid C, Bennett T, Gutjahr C. SMAX1/SMXL2 regulate root and root hair development downstream of KAI2-mediated signalling in Arabidopsis. PLoS Genet 2019; 15:e1008327. [PMID: 31465451 PMCID: PMC6738646 DOI: 10.1371/journal.pgen.1008327] [Citation(s) in RCA: 93] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 09/11/2019] [Accepted: 07/22/2019] [Indexed: 11/18/2022] Open
Abstract
Karrikins are smoke-derived compounds presumed to mimic endogenous signalling molecules (KAI2-ligand, KL), whose signalling pathway is closely related to that of strigolactones (SLs), important regulators of plant development. Both karrikins/KLs and SLs are perceived by closely related α/β hydrolase receptors (KAI2 and D14 respectively), and signalling through both receptors requires the F-box protein MAX2. Furthermore, both pathways trigger proteasome-mediated degradation of related SMAX1-LIKE (SMXL) proteins, to influence development. It has previously been suggested in multiple studies that SLs are important regulators of root and root hair development in Arabidopsis, but these conclusions are based on phenotypes observed in the non-specific max2 mutants and by use of racemic-GR24, a mixture of stereoisomers that activates both D14 and KAI2 signalling pathways. Here, we demonstrate that the majority of the effects on Arabidopsis root development previously attributed to SL signalling are actually mediated by the KAI2 signalling pathway. Using mutants defective in SL or KL synthesis and/or perception, we show that KAI2-mediated signalling alone regulates root hair density and root hair length as well as root skewing, straightness and diameter, while both KAI2 and D14 pathways regulate lateral root density and epidermal cell length. We test the key hypothesis that KAI2 signals by a non-canonical receptor-target mechanism in the context of root development. Our results provide no evidence for this, and we instead show that all effects of KAI2 in the root can be explained by canonical SMAX1/SMXL2 activity. However, we do find evidence for non-canonical GR24 ligand-receptor interactions in D14/KAI2-mediated root hair development. Overall, our results demonstrate that the KAI2 signalling pathway is an important new regulator of root hair and root development in Arabidopsis and lay an important basis for research into a molecular understanding of how very similar and partially overlapping hormone signalling pathways regulate different phenotypic outputs.
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Affiliation(s)
- José Antonio Villaécija-Aguilar
- Faculty of Biology, Genetics, LMU Munich, Biocenter Martinsried, Martinsried, Germany
- Plant Genetics, TUM School of Life Sciences Weihenstephan, Technical University of Munich (TUM), Freising, Germany
| | - Maxime Hamon-Josse
- School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Samy Carbonnel
- Faculty of Biology, Genetics, LMU Munich, Biocenter Martinsried, Martinsried, Germany
- Plant Genetics, TUM School of Life Sciences Weihenstephan, Technical University of Munich (TUM), Freising, Germany
| | - Annika Kretschmar
- Faculty of Biology, Genetics, LMU Munich, Biocenter Martinsried, Martinsried, Germany
| | - Christian Schmidt
- Chair of Food Chemistry and Molecular Sensory Science, TUM School of Life Sciences Weihenstephan, Technical University of Munich (TUM), Freising, Germany
| | - Corinna Dawid
- Chair of Food Chemistry and Molecular Sensory Science, TUM School of Life Sciences Weihenstephan, Technical University of Munich (TUM), Freising, Germany
| | - Tom Bennett
- School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Sainsbury Laboratory Cambridge University, Cambridge, United Kingdom
- * E-mail: (TB); (CG)
| | - Caroline Gutjahr
- Faculty of Biology, Genetics, LMU Munich, Biocenter Martinsried, Martinsried, Germany
- Plant Genetics, TUM School of Life Sciences Weihenstephan, Technical University of Munich (TUM), Freising, Germany
- * E-mail: (TB); (CG)
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