TY - GEN A1 - Huu, Cuong Nguyen A1 - Plaschil, Sylvia A1 - Himmelbach, Axel A1 - Kappel, Christian A1 - Lenhard, Michael T1 - Female self-incompatibility type in heterostylous Primula is determined by the brassinosteroid-inactivating cytochrome P450 CYP734A50 T2 - Current biology N2 - Most flowering plants are hermaphrodites, with flowers having both male and female reproductive organs. One widespread adaptation to limit self-fertilization is self-incompatibility (SI), where self-pollen fails to fertilize ovules.(1,2) In homomorphic SI, many morphologically indistinguishable mating types are found, although in heteromorphic SI, the two or three mating types are associated with different floral morphologies.(3-6) In heterostylous Primula, a hemizygous supergene determines a short-styled S-morph and a long-styled L-morph, corresponding to two different mating types, and full seed set only results from inter morph crosses.(7-9) Style length is controlled by the brassinosteroid (BR)-inactivating cytochrome P450 CYP734A50,(10) yet it remains unclear what defines the male and female incompatibility types. Here, we show that CYP734A50 also determines the female incompatibility type. Inactivating CYP734A50 converts short S-morph styles into long styles with the same incompatibility behavior as L-morph styles, and this effect can be mimicked by exogenous BR treatment. In vitro responses of S-and L-morph pollen grains and pollen tubes to increasing BR levels could only partly explain their different in vivo behavior, suggesting both direct and indirect effects of the different BR levels in S-versus L-morph stigmas and styles in controlling pollen performance. This BR-mediated SI provides a novel mechanism for preventing self-fertilization. The joint control of morphology and SI by CYP734A50 has important implications for the evolutionary buildup of the heterostylous syndrome and provides a straightforward explanation for why essentially all of the derived self-compatible homostylous Primula species are long homostyles.(11) KW - heteromorphic self-incompatibility KW - heterostyly KW - Primula forbesii KW - brassinosteroid KW - CYP734A50 KW - supergene KW - pleiotropy Y1 - 2022 U6 - https://doi.org/10.1016/j.cub.2021.11.046 SN - 0960-9822 SN - 1879-0445 VL - 32 IS - 3 SP - 671 EP - 676, E1-E5 PB - Cell Press CY - Cambridge, Mass. ER - TY - JOUR A1 - Kappel, Christian A1 - Cuong Nguyen Huu, A1 - Lenhard, Michael T1 - A short story gets longer: recent insights into the molecular basis of heterostyly JF - Journal of experimental botany N2 - Heterostyly is a fascinating adaptation to promote outbreeding and a classical paradigm of botany. In the most common type of heterostyly, plants either form flowers with long styles and short stamens, or short styles and long stamens. This reciprocal organ positioning reduces pollen wastage and promotes cross-pollination, thus increasing male fitness. In addition, in many heterostylous species selfing and the generation of unfit progeny due to inbreeding depression is limited by a self-incompatibility system, thus promoting female fitness. The two floral forms are genetically determined by the S locus as a complex supergene, namely a chromosomal region containing several individual genes that control the different traits, such as style or stamen length, and are held together by very tight linkage due to suppressed recombination. Recent molecular-genetic studies in several systems, including Turnera, Fagopyrum, Linum, and Primula have begun to identify and characterize the causal heterostyly genes residing at the S locus. An emerging theme from several families is that the dominant S haplotype represents a hemizygous region not present on the recessive s haplotype. This provides an explanation for the suppressed recombination and suggests a scenario for the chromosomal evolution of the S locus. In this review, we discuss the results from recent molecular-genetic analyses in light of the classical models on the genetics and evolution of heterostyly. KW - CYP734A50 KW - distyly KW - GLOBOSA2 KW - hemizygosity KW - heterostyly KW - Primula KW - S locus KW - supergene KW - tristyly Y1 - 2017 U6 - https://doi.org/10.1093/jxb/erx387 SN - 0022-0957 SN - 1460-2431 VL - 68 SP - 5719 EP - 5730 PB - Oxford Univ. Press CY - Oxford ER -