Ramanauskas Karolis, Jiménez-López Francisco J, Sánchez-Cabrera Mercedes, Escudero Marcial, Ortiz Pedro L, Arista Montserrat, Igić Boris
Department of Biological Sciences, University of Illinois at Chicago, Chicago, 60607, IL, USA.
Departamento de Biología Vegetal y Ecología, Universidad de Sevilla, Apdo. 1095, Sevilla, 41080, Spain.
Am J Bot. 2025 Jan;112(1):e16449. doi: 10.1002/ajb2.16449. Epub 2025 Jan 13.
Primroses famously employ a system that simultaneously expresses distyly and filters out self-pollen. Other species in the Primulaceae family, including Lysimachia monelli (blue pimpernel), also express self-incompatibility (SI), but involving a system with distinct features and an unknown molecular genetic basis.
We utilize a candidate-based transcriptome sequencing (RNA-seq) approach, relying on candidate T2/S-RNase Class III and S-linked F-box-motif-containing genes and harnessing the unusual evolutionary and genetic features of SI, to examine whether an RNase-based mechanism underlies SI in L. monelli. We term this approach "SI detection with RNA-seq" (SIDR).
The results of sequencing, crossing, population genetics, and molecular evolutionary features each support a causal association linking the recovered genotypes with SI phenotypes. The finding of RNase-based SI in Primulaceae (Ericales) all but cements the long-held view that this mechanism was present in the ancestral pentapetal eudicot, whose descendants now comprise two-thirds of angiosperms. It also significantly narrows the plausible maximum age for the heterostyly evolution within the family.
SIDR is powerful, flexible, inexpensive, and most critically enables work in often-neglected species. It may be used with or without candidate genes to close enormous gaps in understanding the genetic basis of SI and the history of breeding system evolution.
报春花以一种同时表现出花柱异长并过滤自身花粉的系统而闻名。报春花科的其他物种，包括蓝点珍珠菜，也表现出自交不亲和性（SI），但涉及一个具有独特特征且分子遗传基础未知的系统。
我们采用基于候选基因的转录组测序（RNA测序）方法，依靠候选的III类T2/S - 核糖核酸酶基因和含S - 连锁F - 盒基序的基因，并利用SI不寻常的进化和遗传特征，来研究基于核糖核酸酶的机制是否是蓝点珍珠菜SI的基础。我们将这种方法称为“通过RNA测序进行SI检测”（SIDR）。
测序、杂交、群体遗传学和分子进化特征的结果均支持将回收的基因型与SI表型联系起来的因果关联。在报春花科（杜鹃花目）中发现基于核糖核酸酶的SI几乎巩固了长期以来的观点，即这种机制存在于原始的五瓣真双子叶植物中，其后代现在占被子植物的三分之二。它还显著缩小了该科内花柱异长进化的可能最大年龄范围。
SIDR功能强大、灵活、成本低，最关键的是能够在常被忽视的物种中开展研究。它可用于有或没有候选基因的情况，以填补在理解SI的遗传基础和育种系统进化历史方面的巨大空白。
