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A pollen selection system links self and interspecific incompatibility in the Brassicaceae

Abstract

Self-incompatibility and recurrent transitions to self-compatibility have shaped the extant mating systems underlying the nonrandom mating critical for speciation in angiosperms. Linkage between self-incompatibility and speciation is illustrated by the shared pollen rejection pathway between self-incompatibility and interspecific unilateral incompatibility (UI) in the Brassicaceae. However, the pollen discrimination system that activates this shared pathway for heterospecific pollen rejection remains unknown. Here we show that Stigma UI3.1, the genetically identified stigma determinant of UI in Arabidopsis lyrata × Arabidopsis arenosa crosses, encodes the S-locus-related glycoprotein 1 (SLR1). Heterologous expression of A. lyrata or Capsella grandiflora SLR1 confers on some Arabidopsis thaliana accessions the ability to discriminate against heterospecific pollen. Acquisition of this ability also requires a functional S-locus receptor kinase (SRK), whose ligand-induced dimerization activates the self-pollen rejection pathway in the stigma. SLR1 interacts with SRK and interferes with SRK homomer formation. We propose a pollen discrimination system based on competition between basal or ligand-induced SLR1–SRK and SRK–SRK complex formation. The resulting SRK homomer levels would be sensed by the common pollen rejection pathway, allowing discrimination among conspecific self- and cross-pollen as well as heterospecific pollen. Our results establish a mechanistic link at the pollen recognition phase between self-incompatibility and interspecific incompatibility.

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Fig. 1: Interspecific reproductive barriers and analysis of the SUI3.1 candidate gene.
Fig. 2: SLR1 functions in heterospecific pollen discrimination.
Fig. 3: Requirement for both SLR1 and SRK for discrimination against heterospecific pollen.
Fig. 4: The SLR1–SRK interaction and competition between SLR1–SRK and SRK–SRK complexes.
Fig. 5: A pollen discrimination system based on the SLR1–SRK interaction.

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References

  1. Cutter, A. D. Reproductive transitions in plants and animals: selfing syndrome, sexual selection and speciation. New Phytol. 224, 1080–1094 (2019).

    Article  PubMed  Google Scholar 

  2. Pickup, M. et al. Mating system variation in hybrid zones: facilitation, barriers and asymmetries to gene flow. New Phytol. 224, 1035–1047 (2019).

    Article  PubMed  PubMed Central  Google Scholar 

  3. Bedinger, P. A., Broz, A. K., Tovar-Mendez, A. & McClure, B. Pollen–pistil interactions and their role in mate selection. Plant Physiol. 173, 79–90 (2017).

    Article  CAS  PubMed  Google Scholar 

  4. Nasrallah, J. B. Stop and go signals at the stigma–pollen interface of the Brassicaceae. Plant Physiol. 193, 927–948 (2023).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  5. Charlesworth, D., Vekemans, X., Castric, V. & Glemin, S. Plant self-incompatibility systems: a molecular evolutionary perspective. New Phytol. 168, 61–69 (2005).

    Article  CAS  PubMed  Google Scholar 

  6. Nasrallah, J. B. Self-incompatibility in the Brassicaceae: regulation and mechanism of self-recognition. Curr. Top. Dev. Biol. 131, 435–452 (2019).

    Article  PubMed  Google Scholar 

  7. Zhao, H. et al. Origin, loss, and regain of self-incompatibility in angiosperms. Plant Cell 34, 579–596 (2022).

    Article  PubMed  Google Scholar 

  8. Goldberg, E. E. et al. Species selection maintains self-incompatibility. Science 330, 493–495 (2010).

    Article  CAS  PubMed  Google Scholar 

  9. Foxe, J. P. et al. Recent speciation associated with the evolution of selfing in Capsella. Proc. Natl Acad. Sci. USA 106, 5241–5245 (2009).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  10. Kitashiba, H. & Nasrallah, J. B. Self-incompatibility in Brassicaceae crops: lessons for interspecific incompatibility. Breed. Sci. 64, 23–37 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  11. Hiscock, S. J. & Dickinson, H. G. Unilateral incompatibility within the Brassicaceae: further evidence for the involvement of the self-incompatibility (S)-locus. Theor. Appl. Genet. 86, 744–753 (1993).

  12. Lewis, D. & Crowe, L. K. Unilateral interspecific incompatiility in flowering plants. Heredity 12, 233–256 (1958).

    Article  Google Scholar 

  13. Murfett, J. et al. S RNase and interspecific pollen rejection in the genus Nicotiana: multiple pollen-rejection pathways contribute to unilateral incompatibility between self-incompatible and self-compatible species. Plant Cell 8, 943–958 (1996).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  14. Li, W. & Chetelat, R. T. A pollen factor linking inter- and intraspecific pollen rejection in tomato. Science 330, 1827–1830 (2010).

    Article  CAS  PubMed  Google Scholar 

  15. Li, L. et al. Evolution of interspecies unilateral incompatibility in the relatives of Arabidopsis thaliana. Mol. Ecol. 27, 2742–2753 (2018).

    Article  PubMed  Google Scholar 

  16. Huang, J. et al. Stigma receptors control intraspecies and interspecies barriers in Brassicaceae. Nature 614, 303–308 (2023).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  17. Pfennig, K. S. Reinforcement as an initiator of population divergence and speciation. Curr. Zool. 62, 145–154 (2016).

    Article  PubMed  PubMed Central  Google Scholar 

  18. Li, W. & Chetelat, R. T. Unilateral incompatibility gene ui1.1 encodes an S-locus F-box protein expressed in pollen of Solanum species. Proc. Natl Acad. Sci. USA 112, 4417–4422 (2015).

  19. Martin, F. W. The genetic control of unilateral incompatibility between two tomato species. Genetics 56, 391–398 (1967).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  20. Qin, X. et al. A farnesyl pyrophosphate synthase gene expressed in pollen functions in S-RNase-independent unilateral incompatibility. Plant J. 93, 417–430 (2018).

    Article  CAS  PubMed  Google Scholar 

  21. Udagawa, H. et al. Genetic analysis of interspecific incompatibility in Brassica rapa. Theor. Appl. Genet. 121, 689–696 (2010).

    Article  CAS  PubMed  Google Scholar 

  22. Broz, A. K. & Bedinger, P. A. Pollen-pistil interactions as reproductive barriers. Annu. Rev. Plant Biol. 72, 615–639 (2021).

  23. Umbach, A. L., Lalonde, B. A., Kandasamy, M. K., Nasrallah, J. B. & Nasrallah, M. E. Immunodetection of protein glycoforms encoded by two independent genes of the self-incompatibility multigene family of Brassica. Plant Physiol. 93, 739–747 (1990).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  24. Naithani, S., Chookajorn, T., Ripoll, D. R. & Nasrallah, J. B. Structural modules for receptor dimerization in the S-locus receptor kinase extracellular domain. Proc. Natl Acad. Sci. USA 104, 12211–12216 (2007).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  25. Lalonde, B. A. et al. A highly conserved Brassica gene with homology to the S-locus-specific glycoprotein structural gene. Plant Cell 1, 249–258 (1989).

    CAS  PubMed  PubMed Central  Google Scholar 

  26. Inaba, R. & Nishio, T. Phylogenetic analysis of Brassiceae based on the nucleotide sequences of the S-locus related gene, SLR1. Theor. Appl. Genet. 105, 1159–1165 (2002).

    Article  CAS  PubMed  Google Scholar 

  27. Franklin, T. M., Oldknow, J. & Trick, M. SLR1 function is dispensable for both self-incompatible rejection and self-compatible pollination processes in Brassica. Sex. Plant Reprod. 9, 203–208 (1996).

    Article  CAS  Google Scholar 

  28. Luu, D. T., Marty-Mazars, D., Trick, M., Dumas, C. & Heizmann, P. Pollen-stigma adhesion in Brassica spp involves SLG and SLR1 glycoproteins. Plant Cell 11, 251–262 (1999).

    CAS  PubMed  PubMed Central  Google Scholar 

  29. Nasrallah, M. E., Liu, P., Sherman-Broyles, S., Boggs, N. A. & Nasrallah, J. B. Natural variation in expression of self-incompatibility in Arabidopsis thaliana: implications for the evolution of selfing. Proc. Natl Acad. Sci. USA 101, 16070–16074 (2004).

  30. Tsuchimatsu, T. et al. Evolution of self-compatibility in Arabidopsis by a mutation in the male specificity gene. Nature 464, 1342–1346 (2010).

    Article  CAS  PubMed  Google Scholar 

  31. Liu, P., Sherman-Broyles, S., Nasrallah, M. E. & Nasrallah, J. B. A cryptic modifier causing transient self-incompatibility in Arabidopsis thaliana. Curr. Biol. 17, 734–740 (2007).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  32. Sherman-Broyles, S. et al. S locus genes and the evolution of self-fertility in Arabidopsis thaliana. Plant Cell 19, 94–106 (2007).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  33. Rea, A. C., Liu, P. & Nasrallah, J. B. A transgenic self-incompatible Arabidopsis thaliana model for evolutionary and mechanistic studies of crucifer self-incompatibility. J. Exp. Bot. 61, 1897–1906 (2010).

    Article  CAS  PubMed  Google Scholar 

  34. Nasrallah, M. E., Liu, P. & Nasrallah, J. B. Generation of self-incompatible Arabidopsis thaliana by transfer of two S locus genes from A. lyrata. Science 297, 247–249 (2002).

    Article  CAS  PubMed  Google Scholar 

  35. Fujii, S. et al. A stigmatic gene confers interspecies incompatibility in the Brassicaceae. Nat. Plants 5, 731–741 (2019).

    Article  CAS  PubMed  Google Scholar 

  36. Murase, K. et al. Mechanism of self/nonself-discrimination in Brassica self-incompatibility. Nat. Commun. 11, 4916 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  37. Ma, R. et al. Structural basis for specific self-incompatibility response in Brassica. Cell Res. 12, 1320–1329 (2016).

    Article  Google Scholar 

  38. Giranton, J. L., Dumas, C., Cock, J. M. & Gaude, T. The integral membrane S-locus receptor kinase of Brassica has serine/threonine kinase activity in a membranous environment and spontaneously forms oligomers in planta. Proc. Natl Acad. Sci. USA 97, 3759–3764 (2000).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  39. Shimosato, H. et al. Characterization of the SP11/SCR high-affinity binding site involved in self/nonself recognition in Brassica self-incompatibility. Plant Cell 19, 107–117 (2007).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  40. Zhang, L. et al. FERONIA receptor kinase-regulated reactive oxygen species mediate self-incompatibility in Brassica rapa. Curr. Biol. 31, 3004–3016.e3004 (2021).

    Article  CAS  PubMed  Google Scholar 

  41. Fujii, S., Kubo, K. & Takayama, S. Non-self- and self-recognition models in plant self-incompatibility. Nat. Plants 2, 16130 (2016).

    Article  CAS  PubMed  Google Scholar 

  42. Turelli, M. & Moyle, L. C. Asymmetric postmating isolation: Darwina’s corollary to Haldanea’s rule. Genetics 176, 1059–1088 (2007).

    Article  PubMed  PubMed Central  Google Scholar 

  43. Bechtold, N., Ellis, J. & Pelletier, G. In planta Agrobacterium mediated gene transfer by infiltration of adult Arabidopsis thaliana plants. C. R. Acad. Sci. 316, 1194–1199 (1993).

    CAS  Google Scholar 

  44. Smyth, D. R., Bowman, J. L. & Meyerowitz, E. M. Early flower development in Arabidopsis. Plant Cell 2, 755–767 (1990).

    CAS  PubMed  PubMed Central  Google Scholar 

  45. Liu, H. et al. Ethylene signaling is required for the acceleration of cell death induced by the activation of AtMEK5 in Arabidopsis. Cell Res. 18, 422–432 (2008).

    Article  CAS  PubMed  Google Scholar 

  46. Waadt, R. et al. Multicolor bimolecular fluorescence complementation reveals simultaneous formation of alternative CBL/CIPK complexes in planta. Plant J. 56, 505–516 (2008).

    Article  CAS  PubMed  Google Scholar 

  47. Kubiasova, K. et al. Cytokinin fluoroprobe reveals multiple sites of cytokinin perception at plasma membrane and endoplasmic reticulum. Nat. Commun. 11, 4285 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  48. Emms, D. M. & Kelly, S. OrthoFinder: phylogenetic orthology inference for comparative genomics. Genome Biol. 20, 238 (2019).

    Article  PubMed  PubMed Central  Google Scholar 

  49. Tamura, K., Stecher, G., Peterson, D., Filipski, A. & Kumar, S. MEGA6: molecular evolutionary genetics analysis version 6.0. Mol. Biol. Evol. 30, 2725–2729 (2013).

  50. Guo, Y. L., Zhao, X., Lanz, C. & Weigel, D. Evolution of the S-locus region in Arabidopsis relatives. Plant Physiol. 157, 937–946 (2011).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  51. Yang, Z. PAML 4: phylogenetic analysis by maximum likelihood. Mol. Biol. Evol. 24, 1586–1591 (2007).

    Article  CAS  PubMed  Google Scholar 

  52. Yang, Z., Wong, W. S. & Nielsen, R. Bayes empirical Bayes inference of amino acid sites under positive selection. Mol. Biol. Evol. 22, 1107–1118 (2005).

    Article  CAS  PubMed  Google Scholar 

  53. Boggs, N. A., Nasrallah, J. B. & Nasrallah, M. E. Independent S-locus mutations caused self-fertility in Arabidopsis thaliana. PLoS Genet. 5, e1000426 (2009).

    Article  PubMed  PubMed Central  Google Scholar 

  54. Tang, C. et al. The evolution of selfing in Arabidopsis thaliana. Science 317, 1070–1072 (2007).

    Article  CAS  PubMed  Google Scholar 

Download references

Acknowledgements

We thank NASC and ABRC for providing A. thaliana, B. oleracea and B. rapa seeds; L. Comai (University of California Davis) for providing A. arenosa seeds; and J. Kudla (Universität Münster) for providing vectors for BIFC assays. This work was supported by the Natural Science Foundation of China (NSFC) (numbers 32170353, 32370234, 31970310 and 32100269), Major Research Plan from the Ministry of Science and Technology of China (number 2013CB945100) and Program for New Century Excellent Talents in University (NECT-08-0529) to P.L.

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B.L., M.L., W.L., Q.C. and H.Z. performed the construction of plasmids, transformation of A. thaliana, analyses of the progenies of the transformants and pollination assays. B.L. performed Co-IP. M.L. and J.Q. performed BIFC experiments. J.X. performed bioinformatic analyses. P.L. designed the study and wrote the paper. J.B.N., M.E.N. and Y.X. were involved in designing the experiments and writing the paper.

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Correspondence to Pei Liu.

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Extended data

Extended Data Fig. 1 Alignment of the protein sequences and domain architecture of SLR1 and eSRK from eight Arabidopsis, Capsella, and Brassica species.

The alignments of representative SLR1 sequences (upper panel) and eSRK + transmembrane (TM) sequences (lower panel) from A. lyrata (Al), A. halleri (Ah), A. thaliana (At), A. arenosa (Aa), C. grandiflora (Cg), B. rapa (Br), and B. oleracea (Bo) are shown. The domain architecture of SLR1 and eSRK proteins and their 12 conserved cysteine residues, which are characteristic of the so-called S-domain (SD) protein family, are shown above the alignments. Also shown for eSRKs are the hypervariable (hv) regions which contain most residues responsible for the binding of SRK with SCR (purple dots) and residues involved in SRK homodimerization (blue dots) as determined from the high-resolution crystal structure of the eSRK-SCR complex41.

Extended Data Fig. 2 The gene tree of SLR1, but not that of SRK proteins, is concordant with the species tree in representative Brassicaceae species.

The gene tree includes SLR1 and SRK proteins from representative Brassicaceae species. The blue filled triangles mark A. thaliana and B. rapa for which nineteen and four SLR1 alleles have been reported, respectively. To the right of the gene tree, the colored circles represent A. lyrata (Al; blue), A. halleri (Ah; azure), A. arenosa (Aa; yellow), A. thaliana (At; grey), C. grandiflora (Cg; pink), C. rubella (Cr; black), B. rapa (Br; red), and B. oleracea (Bo; purple), and the self-incompatible (SI) or self-compatible (SC) state of each species is indicated in parentheses. The species tree (in blue) was constructed by the coalesced sequences (3,778) of genome-wide single-copy orthogroups. The bootstrap values and genetic distance are shown.

Extended Data Fig. 3 The AlSLR1 transgene confers the ability to discriminate against A. arenosa pollen on the stigmas of the A. thaliana Old-1 accession.

Microscopic images of pollinated stigmas (a) and the number of pollen tubes per stigma (b) observed in a representative T1 Old-1:AlSR1 plant. The germination and tube growth of A. arenosa pollen observed on wild-type Old-1 stigmas were largely abolished in Old-1:AlSLR1 plants on stage-13 but not stage-14 stigmas. Thus, the interspecific incompatibility acquired by Old-1 was transient as for Wei-1 (Extended Data Table 1). The incompatibility response of Old-1:AlSLR1 was weaker than that of Wei-1:AlSLR1 (Figs. 2b and 2c), as Old-1:AlSLR1 stigmas supported the growth of a somewhat larger number pollen tubes on the stigma papilla cells. Scale bars, 50 μm. The dots indicate individual data points. Error bars are ± SEM, n (in cyan) indicates the number of stigmas. *P < 0.05 (two-tailed Students t-test). Each experiment was repeated at least three times with consistent results.

Extended Data Fig. 4 The AlSLR1 transgene does not confer the ability to discriminate against A. arenosa pollen on the stigmas of the A. thaliana Col-0, Ws, and Mt-0 accessions.

a,b,c The microscopic images to the left show that the germination and tube growth of A. arenosa pollen on A. thaliana stigmas were not significantly altered by expression of the AlSLR1 transgene in Col-0 (a), Ws (b), and Mt-0 (c). This conclusion was confirmed by the number of pollen tubes observed per stigma in 12, 13 and 14 stage flowers as shown in the graphs to the right. The results of manual pollinations are shown for a representative T1 transgenic plant of each of the three accessions. Similar results were also observed in AlSLR1 transformants of the RLD, No, Nd-0, and C24 accessions (see Extended Data Table 1, Figs. 3b and 3c). Scale bars, 50 μm. The dots indicate individual data points. Error bars are ± SEM, n (in cyan) indicates the number of stigmas. Each experiment was repeated at least three times with consistent results.

Extended Data Table 1 The effect of expressing AlSLR1 on the ability of stigmas to reject A. arenosa pollen in nine A. thaliana accessions differing in both the genetics of self-fertility and the phenotype resulting from attempts to restore self-incompatibility
Extended Data Table 2 The diverse outcomes in reciprocal crosses of a species pair are determined by the presence or absence in each species of three factors required for UI

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Unprocessed gels for Fig. 4a.

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Liu, B., Li, M., Qiu, J. et al. A pollen selection system links self and interspecific incompatibility in the Brassicaceae. Nat Ecol Evol 8, 1129–1139 (2024). https://doi.org/10.1038/s41559-024-02399-4

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