Biewer-Heisler Timothy J, Gibson Matthew J S, Sornay Emily, Moyle Leonie C
Department of Biology, Indiana University, 1001 E 3rd St Room 325, Bloomington, IN 47405, USA.
G3 (Bethesda). 2025 Jul 9;15(7). doi: 10.1093/g3journal/jkaf107.
Postmating prezygotic (PMPZ) traits play an important role in mating success, especially in species where gametes from multiple males compete. Despite this, the effect of mating system transitions, and attendant shifts in the intensity of sexual selection, on specific PMPZ traits and loci is still poorly understood. Here, we assessed differences in pollen PMPZ traits and tissue-specific gene expression (in leaf, pollen, and style) between 2 closely related plant species with different mating systems-Solanum lycopersicum (selfing) and Solanum pennellii (outcrossing). We focused on species differences in loci with known roles in pollen tube growth rate, including pectin methylesterases (PMEs) and their inhibitors (PMEIs), and in vitro and in vivo pollen tube growth rates. Among the gene expression differences observed between species, we found that the expression domain of pollen-biased genes was much narrower in the selfing species S. lycopersicum compared with the outcrossing species S. pennellii, including for most reproductive PMEs and PMEIs. In addition, S. pennellii had faster pollen tube growth rates in vivo, while S. lycopersicum had faster in vitro pollen tube growth rates. We propose that the lower expression of pollen tube development genes in S. lycopersicum style tissue, and reduced in vivo pollen performance, is a result of reduced allocation to stylar mechanisms that modulate pollen tube growth, potentially consistent with relaxed selection on cryptic female choice in the selfing species.
交配后合子前（PMPZ）性状在交配成功中起着重要作用，尤其是在多个雄性的配子相互竞争的物种中。尽管如此，交配系统转变以及随之而来的性选择强度变化对特定PMPZ性状和基因座的影响仍知之甚少。在这里，我们评估了两种具有不同交配系统的近缘植物物种——番茄（自交）和彭氏茄（异交）之间花粉PMPZ性状和组织特异性基因表达（在叶片、花粉和花柱中）的差异。我们重点研究了在花粉管生长速率中起已知作用的基因座的物种差异，包括果胶甲基酯酶（PMEs）及其抑制剂（PMEIs），以及体外和体内花粉管生长速率。在观察到的物种间基因表达差异中，我们发现与异交物种彭氏茄相比，自交物种番茄中花粉偏向基因的表达域要窄得多，包括大多数生殖相关的PMEs和PMEIs。此外，彭氏茄在体内的花粉管生长速率更快，而番茄在体外的花粉管生长速率更快。我们认为，番茄花柱组织中花粉管发育基因的低表达以及体内花粉性能的降低，是由于对调节花粉管生长的花柱机制的分配减少所致，这可能与自交物种中隐性雌性选择上的选择放松相一致。
