{"title":"The evolution of self-fertility in apomictic plants.","authors":"Elvira Hörandl","doi":"10.1007/s00497-009-0122-3","DOIUrl":null,"url":null,"abstract":"<p><p>Self-fertilization and apomixis have often been seen as alternative evolutionary strategies of flowering plants that are advantageous for colonization scenarios and in bottleneck situations. Both traits have multiple origins, but different genetic control mechanisms; possible connections between the two phenomena have long been overlooked. Most apomictic plants, however, need a fertilization of polar nuclei for normal seed development (pseudogamy). If self-pollen is used for this purpose, self-compatibility is a requirement for successful pollen tube growth. Apomictic lineages usually evolve from sexual self-incompatible outcrossing plants, but pseudogamous apomicts frequently show a breakdown of self-incompatibility. Two possible pathways may explain the evolution of SC: (1) Polyploidy not only may trigger gametophytic apomixis, but also may result in a partial breakdown of SI systems. (2) Alternatively, frequent pseudo self-compatibility (PSC) via aborted pollen may induce selfing of pseudogamous apomicts (mentor effects). Self-fertile pseudogamous genotypes will be selected for within mixed sexual-apomictic populations because of avoidance of interploidal crosses; in founder situations, SC provides reproductive assurance independent from pollinators and mating partners. SI pseudogamous genotypes will be selected against in mixed populations because of minority cytotype problems and high pollen discounting; in founder populations, SI reactions among clone mates will reduce seed set. Selection for SC genotypes will eliminate SI unless the apomict maintains a high genotypic diversity and thus a diversity of S-alleles within a population, or shifts to pollen-independent autonomous apomixis. The implications of a breakdown of SI in apomictic plants for evolutionary questions and for agricultural sciences are being discussed.</p>","PeriodicalId":21770,"journal":{"name":"Sexual Plant Reproduction","volume":"23 1","pages":"73-86"},"PeriodicalIF":0.0000,"publicationDate":"2010-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2854795/pdf/ukmss-29603.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Sexual Plant Reproduction","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1007/s00497-009-0122-3","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2009/11/20 0:00:00","PubModel":"Epub","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
Self-fertilization and apomixis have often been seen as alternative evolutionary strategies of flowering plants that are advantageous for colonization scenarios and in bottleneck situations. Both traits have multiple origins, but different genetic control mechanisms; possible connections between the two phenomena have long been overlooked. Most apomictic plants, however, need a fertilization of polar nuclei for normal seed development (pseudogamy). If self-pollen is used for this purpose, self-compatibility is a requirement for successful pollen tube growth. Apomictic lineages usually evolve from sexual self-incompatible outcrossing plants, but pseudogamous apomicts frequently show a breakdown of self-incompatibility. Two possible pathways may explain the evolution of SC: (1) Polyploidy not only may trigger gametophytic apomixis, but also may result in a partial breakdown of SI systems. (2) Alternatively, frequent pseudo self-compatibility (PSC) via aborted pollen may induce selfing of pseudogamous apomicts (mentor effects). Self-fertile pseudogamous genotypes will be selected for within mixed sexual-apomictic populations because of avoidance of interploidal crosses; in founder situations, SC provides reproductive assurance independent from pollinators and mating partners. SI pseudogamous genotypes will be selected against in mixed populations because of minority cytotype problems and high pollen discounting; in founder populations, SI reactions among clone mates will reduce seed set. Selection for SC genotypes will eliminate SI unless the apomict maintains a high genotypic diversity and thus a diversity of S-alleles within a population, or shifts to pollen-independent autonomous apomixis. The implications of a breakdown of SI in apomictic plants for evolutionary questions and for agricultural sciences are being discussed.
自花受精和无花受精常常被视为有花植物的另一种进化策略,在殖民地化和瓶颈情况下具有优势。这两种特性有多种起源,但遗传控制机制不同;长期以来,这两种现象之间可能存在的联系一直被忽视。然而,大多数无花植物需要极核受精才能正常发育种子(假两性)。如果自花粉被用于这一目的,那么自相容性就是花粉管成功生长的必要条件。自交系通常是从有性自交不相容的外交植物进化而来,但假两性自交系经常出现自交不相容的崩溃。有两种可能的途径可以解释自交系的进化:(1)多倍体不仅可能引发配子体的无性繁殖,还可能导致自交系的部分崩溃。(2)另外,通过流产花粉频繁产生的假自交(PSC)可能会诱发假两性无性繁殖的自交(导师效应)。在有性-无性繁殖混合种群中,自交假两性基因型将被选育出来,因为它们可以避免叶间杂交;在创始人情况下,自交假两性基因型提供了不受授粉者和交配对象影响的生殖保证。由于少数细胞型问题和高花粉折扣率,SI 假两性基因型将在混合种群中被淘汰;在始祖种群中,克隆配偶间的 SI 反应将降低种子的结实率。对SC基因型的选择将消除SI,除非无花果在种群中保持较高的基因型多样性,从而保持S-等位基因的多样性,或转向不依赖花粉的自主无花果混交。我们正在讨论有袋类植物中 SI 的破坏对进化问题和农业科学的影响。