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Castric V, Batista RA, Carré A, Mousavi S, Mazoyer C, Godé C, Gallina S, Ponitzki C, Theron A, Bellec A, Marande W, Santoni S, Mariotti R, Rubini A, Legrand S, Billiard S, Vekemans X, Vernet P, Saumitou-Laprade P. The homomorphic self-incompatibility system in Oleaceae is controlled by a hemizygous genomic region expressing a gibberellin pathway gene. Curr Biol 2024; 34:1967-1976.e6. [PMID: 38626763 DOI: 10.1016/j.cub.2024.03.047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 02/29/2024] [Accepted: 03/25/2024] [Indexed: 04/18/2024]
Abstract
In flowering plants, outcrossing is commonly ensured by self-incompatibility (SI) systems. These can be homomorphic (typically with many different allelic specificities) or can accompany flower heteromorphism (mostly with just two specificities and corresponding floral types). The SI system of the Oleaceae family is unusual, with the long-term maintenance of only two specificities but often without flower morphology differences. To elucidate the genomic architecture and molecular basis of this SI system, we obtained chromosome-scale genome assemblies of Phillyrea angustifolia individuals and related them to a genetic map. The S-locus region proved to have a segregating 543-kb indel unique to one specificity, suggesting a hemizygous region, as observed in all distylous systems so far studied at the genomic level. Only one of the predicted genes in this indel region is found in the olive tree, Olea europaea, genome, also within a segregating indel. We describe complete association between the presence/absence of this gene and the SI types determined for individuals of seven distantly related Oleaceae species. This gene is predicted to be involved in catabolism of the gibberellic acid (GA) hormone, and experimental manipulation of GA levels in developing buds modified the male and female SI responses of the two specificities in different ways. Our results provide a unique example of a homomorphic SI system, where a single conserved gibberellin-related gene in a hemizygous indel underlies the long-term maintenance of two groups of reproductive compatibility.
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Affiliation(s)
- Vincent Castric
- Univ. Lille, CNRS, UMR 8198, Evo-Eco-Paleo, F-59000 Lille, France
| | - Rita A Batista
- Univ. Lille, CNRS, UMR 8198, Evo-Eco-Paleo, F-59000 Lille, France
| | - Amélie Carré
- Univ. Lille, CNRS, UMR 8198, Evo-Eco-Paleo, F-59000 Lille, France
| | - Soraya Mousavi
- CNR, Institute of Biosciences and Bioresources (IBBR), 06128 Perugia, Italy
| | - Clément Mazoyer
- Univ. Lille, CNRS, UMR 8198, Evo-Eco-Paleo, F-59000 Lille, France
| | - Cécile Godé
- Univ. Lille, CNRS, UMR 8198, Evo-Eco-Paleo, F-59000 Lille, France
| | - Sophie Gallina
- Univ. Lille, CNRS, UMR 8198, Evo-Eco-Paleo, F-59000 Lille, France
| | - Chloé Ponitzki
- Univ. Lille, CNRS, UMR 8198, Evo-Eco-Paleo, F-59000 Lille, France
| | - Anthony Theron
- INRAE, CNRGV French Plant Genomic Resource Center, F-31326 Castanet Tolosan, France
| | - Arnaud Bellec
- INRAE, CNRGV French Plant Genomic Resource Center, F-31326 Castanet Tolosan, France
| | - William Marande
- INRAE, CNRGV French Plant Genomic Resource Center, F-31326 Castanet Tolosan, France
| | - Sylvain Santoni
- UMR DIAPC Diversité et adaptation des plantes cultivées, F-34398 Montpellier, France
| | - Roberto Mariotti
- CNR, Institute of Biosciences and Bioresources (IBBR), 06128 Perugia, Italy
| | - Andrea Rubini
- CNR, Institute of Biosciences and Bioresources (IBBR), 06128 Perugia, Italy
| | - Sylvain Legrand
- Univ. Lille, CNRS, UMR 8198, Evo-Eco-Paleo, F-59000 Lille, France
| | - Sylvain Billiard
- Univ. Lille, CNRS, UMR 8198, Evo-Eco-Paleo, F-59000 Lille, France
| | - Xavier Vekemans
- Univ. Lille, CNRS, UMR 8198, Evo-Eco-Paleo, F-59000 Lille, France
| | - Philippe Vernet
- Univ. Lille, CNRS, UMR 8198, Evo-Eco-Paleo, F-59000 Lille, France
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Boucher JJ, Ireland HS, Wang R, David KM, Schaffer RJ. The genetic control of herkogamy. FUNCTIONAL PLANT BIOLOGY : FPB 2024; 51:FP23315. [PMID: 38687848 DOI: 10.1071/fp23315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Accepted: 04/14/2024] [Indexed: 05/02/2024]
Abstract
Herkogamy is the spatial separation of anthers and stigmas within complete flowers, and is a key floral trait that promotes outcrossing in many angiosperms. The degree of separation between pollen-producing anthers and receptive stigmas has been shown to influence rates of self-pollination amongst plants, with a reduction in herkogamy increasing rates of successful selfing in self-compatible species. Self-pollination is becoming a critical issue in horticultural crops grown in environments where biotic pollinators are limited, absent, or difficult to utilise. In these cases, poor pollination results in reduced yield and misshapen fruit. Whilst there is a growing body of work elucidating the genetic basis of floral organ development, the genetic and environmental control points regulating herkogamy are poorly understood. A better understanding of the developmental and regulatory pathways involved in establishing varying degrees of herkogamy is needed to provide insights into the production of flowers more adept at selfing to produce consistent, high-quality fruit. This review presents our current understanding of herkogamy from a genetics and hormonal perspective.
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Affiliation(s)
- Jacques-Joseph Boucher
- The New Zealand Institute for Plant and Food Research Ltd, 55 Old Mill Road, Motueka 7198, New Zealand; and School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Hilary S Ireland
- The New Zealand Institute for Plant and Food Research Ltd, Private Bag 92196, Auckland 1142, New Zealand
| | - Ruiling Wang
- The New Zealand Institute for Plant and Food Research Ltd, Private Bag 92196, Auckland 1142, New Zealand
| | - Karine M David
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Robert J Schaffer
- The New Zealand Institute for Plant and Food Research Ltd, 55 Old Mill Road, Motueka 7198, New Zealand; and School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
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Scheible N, Henning PM, McCubbin AG. Calmodulin-Domain Protein Kinase PiCDPK1 Interacts with the 14-3-3-like Protein NtGF14 to Modulate Pollen Tube Growth. PLANTS (BASEL, SWITZERLAND) 2024; 13:451. [PMID: 38337984 PMCID: PMC10857193 DOI: 10.3390/plants13030451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Revised: 01/29/2024] [Accepted: 02/01/2024] [Indexed: 02/12/2024]
Abstract
Calcium-mediated signaling pathways are known to play important roles in the polar growth of pollen tubes. The calcium-dependent protein kinase, PiCDPK1, has been shown to be involved in regulating this process through interaction with a guanine dissociation inhibitor, PiRhoGDI1. To more fully understand the role of PiCDPK1 in pollen tube extension, we designed a pull-down study to identify additional substrates of this kinase. These experiments identified 123 putative interactors. Two of the identified proteins were predicted to directly interact with PiCDPK1, and this possibility was investigated in planta. The first, NtGF14, a 14-3-3-like protein, did not produce a noticeable phenotype when overexpressed in pollen alone but partially rescued the spherical tube phenotype caused by PiCDPK1 over-expression when co-over-expressed with the kinase. The second, NtREN1, a GTPase activating protein (GAP), severely inhibited pollen tube germination when over-expressed, and its co-over-expression with PiCDPK1 did not substantially affect this phenotype. These results suggest a novel in vivo interaction between NtGF14 and PiCDPK1 but do not support the direct interaction between PiCDPK1 and NtREN1. We demonstrate the utility of the methodology used to identify potential protein interactions while confirming the necessity of additional studies to confirm their validity. Finally, additional support was found for intersection between PiCDPK1 and RopGTPase pathways to control polar growth at the pollen tube tip.
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Affiliation(s)
| | | | - Andrew G. McCubbin
- School of Biological Sciences, Washington State University, Pullman, WA 99164, USA; (N.S.); (P.M.H.)
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Yang J, Xue H, Li Z, Zhang Y, Shi T, He X, Barrett SCH, Wang Q, Chen J. Haplotype-resolved genome assembly provides insights into the evolution of S-locus supergene in distylous Nymphoides indica. THE NEW PHYTOLOGIST 2023; 240:2058-2071. [PMID: 37717220 DOI: 10.1111/nph.19264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Accepted: 08/30/2023] [Indexed: 09/19/2023]
Abstract
Distyly has evolved independently in numerous animal-pollinated angiosperm lineages. Understanding of its molecular basis has been restricted to a few species, primarily Primula. Here, we investigate the genetic architecture of the single diallelic locus (S-locus) supergene, a linkage group of functionally associated genes, and explore how it may have evolved in distylous Nymphoides indica, a lineage of flowering plants not previously investigated. We assembled haplotype-resolved genomes, used read-coverage-based genome-wide association study (rb-GWAS) to locate the S-locus supergene, co-expression network analysis to explore gene networks underpinning the development of distyly, and comparative genomic analyses to investigate the origins of the S-locus supergene. We identified three linked candidate S-locus genes - NinBAS1, NinKHZ2, and NinS1 - that were only evident in the short-styled morph and were hemizygous. Co-expression network analysis suggested that brassinosteroids contribute to dimorphic sex organs in the short-styled morph. Comparative genomic analyses indicated that the S-locus supergene likely evolved via stepwise duplications and has been affected by transposable element activities. Our study provides novel insight into the structure, regulation, and evolution of the supergene governing distyly in N. indica. It also provides high-quality genomic resources for future research on the molecular mechanisms underlying the striking evolutionary convergence in form and function across heterostylous taxa.
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Affiliation(s)
- Jingshan Yang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, 430074, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Haoran Xue
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks St, Toronto, ON, M5S 3B2, Canada
- Institute for Biochemistry and Biology, University of Potsdam, 14476, Potsdam-Golm, Germany
| | - Zhizhong Li
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Yue Zhang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Tao Shi
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Xiangyan He
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, 430074, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Spencer C H Barrett
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks St, Toronto, ON, M5S 3B2, Canada
| | - Qingfeng Wang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, 430074, China
| | - Jinming Chen
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, 430074, China
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Luo Z, Zhao Z, Xu Y, Shi M, Tu T, Pei N, Zhang D. Comprehensive transcriptomic profiling reveals complex molecular mechanisms in the regulation of style-length dimorphism in Guettarda speciosa (Rubiaceae), a species with "anomalous" distyly. FRONTIERS IN PLANT SCIENCE 2023; 14:1116078. [PMID: 37008460 PMCID: PMC10060554 DOI: 10.3389/fpls.2023.1116078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 02/16/2023] [Indexed: 06/19/2023]
Abstract
BACKGROUND The evolution of heterostyly, a genetically controlled floral polymorphism, has been a hotspot of research since the 19th century. In recent years, studies on the molecular mechanism of distyly (the most common form of heterostyly) revealed an evolutionary convergence in genes for brassinosteroids (BR) degradation in different angiosperm groups. This floral polymorphism often exhibits considerable variability that some taxa have significant stylar dimorphism, but anther height differs less. This phenomenon has been termed "anomalous" distyly, which is usually regarded as a transitional stage in evolution. Compared to "typical" distyly, the genetic regulation of "anomalous" distyly is almost unknown, leaving a big gap in our understanding of this special floral adaptation strategy. METHODS Here we performed the first molecular-level study focusing on this floral polymorphism in Guettarda speciosa (Rubiaceae), a tropical tree with "anomalous" distyly. Comprehensive transcriptomic profiling was conducted to examine which genes and metabolic pathways were involved in the genetic control of style dimorphism and if they exhibit similar convergence with "typical" distylous species. RESULTS "Brassinosteroid homeostasis" and "plant hormone signal transduction" was the most significantly enriched GO term and KEGG pathway in the comparisons between L- and S-morph styles, respectively. Interestingly, homologs of all the reported S-locus genes either showed very similar expressions between L- and S-morph styles or no hits were found in G. speciosa. BKI1, a negative regulator of brassinosteroid signaling directly repressing BRI1 signal transduction, was identified as a potential gene regulating style length, which significantly up-regulated in the styles of S-morph. DISCUSSION These findings supported the hypothesis that style length in G. speciosa was regulated through a BR-related signaling network in which BKI1 may be one key gene. Our data suggested, in species with "anomalous" distyly, style length was regulated by gene differential expressions, instead of the "hemizygous" S-locus genes in "typical" distylous flowers such as Primula and Gelsemium, representing an "intermediate" stage in the evolution of distyly. Genome-level analysis and functional studies in more species with "typical" and "anomalous" distyly would further decipher this "most complex marriage arrangement" in angiosperms and improve our knowledge of floral evolution.
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Affiliation(s)
- Zhonglai Luo
- School of Life Sciences and Medicine, Shandong University of Technology, Zibo, China
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Zhongtao Zhao
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Yuanqing Xu
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Miaomiao Shi
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Tieyao Tu
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Nancai Pei
- Research Institute of Tropical Forestry, Chinese Academy of Forestry, Guangzhou, China
| | - Dianxiang Zhang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
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Henning PM, Roalson EH, Mir W, McCubbin AG, Shore JS. Annotation of the Turnera subulata (Passifloraceae) Draft Genome Reveals the S-Locus Evolved after the Divergence of Turneroideae from Passifloroideae in a Stepwise Manner. PLANTS (BASEL, SWITZERLAND) 2023; 12:286. [PMID: 36679000 PMCID: PMC9862265 DOI: 10.3390/plants12020286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 12/27/2022] [Accepted: 01/03/2023] [Indexed: 06/17/2023]
Abstract
A majority of Turnera species (Passifloraceae) exhibit distyly, a reproductive system involving both self-incompatibility and reciprocal herkogamy. This system differs from self-incompatibility in Passiflora species. The genetic basis of distyly in Turnera is a supergene, restricted to the S-morph, and containing three S-genes. How supergenes and distyly evolved in Turnera, and the other Angiosperm families exhibiting distyly remain largely unknown. Unraveling the evolutionary origins in Turnera requires the generation of genomic resources and extensive phylogenetic analyses. Here, we present the annotated draft genome of the S-morph of distylous Turnera subulata. Our annotation allowed for phylogenetic analyses of the three S-genes' families across 56 plant species ranging from non-seed plants to eudicots. In addition to the phylogenetic analysis, we identified the three S-genes' closest paralogs in two species of Passiflora. Our analyses suggest that the S-locus evolved after the divergence of Passiflora and Turnera. Finally, to provide insights into the neofunctionalization of the S-genes, we compared expression patterns of the S-genes with close paralogs in Arabidopsis and Populus trichocarpa. The annotation of the T. subulata genome will provide a useful resource for future comparative work. Additionally, this work has provided insights into the convergent nature of distyly and the origin of supergenes.
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Affiliation(s)
- Paige M. Henning
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
- Center for Genomic Science Innovation, University of Wisconsin Madison, 425 Henry Mall, Madison, WI 53706-1577, USA
| | - Eric H. Roalson
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - Wali Mir
- Department of Biology, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada
| | - Andrew G. McCubbin
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - Joel S. Shore
- Department of Biology, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada
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Comparative transcriptomics reveals commonalities and differences in the genetic underpinnings of a floral dimorphism. Sci Rep 2022; 12:20771. [PMID: 36456708 PMCID: PMC9715534 DOI: 10.1038/s41598-022-25132-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 11/25/2022] [Indexed: 12/05/2022] Open
Abstract
Distyly, a floral dimorphism associated with heteromorphic self-incompatibility and controlled by the S-locus supergene, evolved independently multiple times. Comparative analyses of the first transcriptome atlas for the main distyly model, Primula veris, with other distylous species produced the following findings. A set of 53 constitutively expressed genes in P. veris did not include any of the housekeeping genes commonly used to normalize gene expression in qPCR experiments. The S-locus gene CYPT acquired its role in controlling style elongation via a change in expression profile. Comparison of genes differentially expressed between floral morphs revealed that brassinosteroids and auxin are the main hormones controlling style elongation in P. veris and Fagopyrum esculentum, respectively. Furthermore, shared biochemical pathways might underlie the expression of distyly in the distantly related P. veris, F. esculentum and Turnera subulata, suggesting a degree of correspondence between evolutionary convergence at phenotypic and molecular levels. Finally, we provide the first evidence supporting the previously proposed hypothesis that distyly supergenes of distantly related species evolved via the recruitment of genes related to the phytochrome-interacting factor (PIF) signaling network. To conclude, this is the first study that discovered homologous genes involved in the control of distyly in distantly related taxa.
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Henning PM, Shore JS, McCubbin AG. The S-Gene YUC6 Pleiotropically Determines Male Mating Type and Pollen Size in Heterostylous Turnera (Passifloraceae): A Novel Neofunctionalization of the YUCCA Gene Family. PLANTS (BASEL, SWITZERLAND) 2022; 11:2640. [PMID: 36235506 PMCID: PMC9572539 DOI: 10.3390/plants11192640] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 09/27/2022] [Accepted: 10/05/2022] [Indexed: 06/16/2023]
Abstract
In heterostylous, self-incompatible Turnera species, a member of the YUCCA gene family, YUC6, resides at the S-locus and has been hypothesized to determine the male mating type. YUCCA gene family members synthesize the auxin, indole-3-acetic acid, via a two-step process involving the TAA gene family. Consequently, it has been speculated that differences in auxin concentration in developing anthers are the biochemical basis underlying the male mating type. Here, we provide empirical evidence that supports this hypothesis. Using a transgenic knockdown approach, we show that YUC6 acts pleiotropically to control both the male physiological mating type and pollen size, but not the filament length dimorphism associated with heterostyly in Turnera. Using qPCR to assess YUC6 expression in different transgenic lines, we demonstrate that the level of YUC6 knockdown correlates with the degree of change observed in the male mating type. Further assessment of YUC6 expression through anther development, in the knockdown lines, suggests that the male mating type is irreversibly determined during a specific developmental window prior to microsporogenesis, which is consistent with the genetically sporophytic nature of this self-incompatibility system. These results represent the first gene controlling male mating type to be characterized in any species with heterostyly.
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Affiliation(s)
- Paige M. Henning
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - Joel S. Shore
- Department of Biology, York University, Toronto, ON M3J 1P3, Canada
| | - Andrew G. McCubbin
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
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Pistil Mating Type and Morphology Are Mediated by the Brassinosteroid Inactivating Activity of the S-Locus Gene BAHD in Heterostylous Turnera Species. Int J Mol Sci 2021; 22:ijms221910603. [PMID: 34638969 PMCID: PMC8509066 DOI: 10.3390/ijms221910603] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Revised: 09/23/2021] [Accepted: 09/28/2021] [Indexed: 01/05/2023] Open
Abstract
Heterostyly is a breeding system that promotes outbreeding through a combination of morphological and physiological floral traits. In Turnera these traits are governed by a single, hemizygous S-locus containing just three genes. We report that the S-locus gene, BAHD, is mutated and encodes a severely truncated protein in a self-compatible long homostyle species. Further, a self-compatible long homostyle mutant possesses a T. krapovickasii BAHD allele with a point mutation in a highly conserved domain of BAHD acyl transferases. Wild type and mutant TkBAHD alleles were expressed in Arabidopsis to assay for brassinosteroid (BR) inactivating activity. The wild type but not mutant allele caused dwarfism, consistent with the wild type possessing, but the mutant allele having lost, BR inactivating activity. To investigate whether BRs act directly in self-incompatibility, BRs were added to in vitro pollen cultures of the two mating types. A small morph specific stimulatory effect on pollen tube growth was found with 5 µM brassinolide, but no genotype specific inhibition was observed. These results suggest that BAHD acts pleiotropically to mediate pistil length and physiological mating type through BR inactivation, and that in regard to self-incompatibility, BR acts by differentially regulating gene expression in pistils, rather than directly on pollen.
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Matzke CM, Shore JS, Neff MM, McCubbin AG. The Turnera Style S-Locus Gene TsBAHD Possesses Brassinosteroid-Inactivating Activity When Expressed in Arabidopsis thaliana. PLANTS 2020; 9:plants9111566. [PMID: 33202834 PMCID: PMC7697239 DOI: 10.3390/plants9111566] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 11/06/2020] [Accepted: 11/11/2020] [Indexed: 11/29/2022]
Abstract
Heterostyly distinct hermaphroditic floral morphs enforce outbreeding. Morphs differ structurally, promote cross-pollination, and physiologically block self-fertilization. In Turnera the self-incompatibility (S)-locus controlling heterostyly possesses three genes specific to short-styled morph genomes. Only one gene, TsBAHD, is expressed in pistils and this has been hypothesized to possess brassinosteroid (BR)-inactivating activity. We tested this hypothesis using heterologous expression in Arabidopsis thaliana as a bioassay, thereby assessing growth phenotype, and the impacts on the expression of endogenous genes involved in BR homeostasis and seedling photomorphogenesis. Transgenic A. thaliana expressing TsBAHD displayed phenotypes typical of BR-deficient mutants, with phenotype severity dependent on TsBAHD expression level. BAS1, which encodes an enzyme involved in BR inactivation, was downregulated in TsBAHD-expressing lines. CPD and DWF, which encode enzymes involved in BR biosynthesis, were upregulated. Hypocotyl growth of TsBAHD dwarfs responded to application of brassinolide in light and dark in a manner typical of plants over-expressing genes encoding BR-inactivating activity. These results provide empirical support for the hypothesis that TsBAHD possesses BR-inactivating activity. Further this suggests that style length in Turnera is controlled by the same mechanism (BR inactivation) as that reported for Primula, but using a different class of enzyme. This reveals interesting convergent evolution in a biochemical mechanism to regulate floral form in heterostyly.
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Affiliation(s)
- Courtney M. Matzke
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA 99164-4236, USA;
| | - Joel S. Shore
- Department of Biology, York University, 4700 Keele Street, Toronto, ON M3J1P3, Canada;
| | - Michael M. Neff
- Department of Crops and Soils, Washington State University, PO Box 644236, Pullman, WA 99164, USA;
| | - Andrew G. McCubbin
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA 99164-4236, USA;
- Correspondence:
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