Date: 13th May 2026
Time: 13:00
Title: Genetic control of pollen size and competitive ability
Location: Seminar room K1088, Viikki Info building, Viikinkaari 11
Host: Roosa Laitinen
Abstract: In flowering plants, pollen size is a key determinant of male reproductive success, yet we know surprisingly little about the genetic basis of natural variation in pollen size and number. In the first part of my talk, I will focus on heterostylous Primula and show how we identified two linked genes within the classic S‑locus supergene as major regulators of the differences in pollen size, pollen number and male self‑incompatibility type between the short‑ and long‑styled morphs. Using an induced deletion, transient gene silencing and transcriptomics, we find that one of these genes acts pre‑meiotically to enlarge pollen precursor cells, so that fewer but larger microspore mother cells enter meiosis, explaining the sporophytic control of morph differences in pollen traits. Loss of the two genes not only produces smaller pollen, but also switches the male SI behaviour towards that of the opposite morph, and competitive pollination experiments demonstrate a clear siring advantage of larger pollen grains. In a second part, I will relate these findings to ongoing work in the outcrossing Brassicaceae species Capsella grandiflora, where we study natural variation in haploid competition. To do so, we use transmission‑ratio distortion mapping to uncover naturally segregating haplotypes that affect pollen competitiveness in wild populations.
We are studying the genetic basis of natural variation in three main areas: floral polymorphisms such as heterostyly or mirror-image flowers; haploid competition; and phenotypic plasticity of plants to environmental conditions and resources. To this end, a range of classical genetic and molecular methods are used.