Confirmation of a Gametophytic Self-Incompatibility in Oryza longistaminata
Xiaoping Lian, Shilai Zhang, Guangfu Huang, Liyu Huang, Jing Zhang, Fengyi Hu
Abstract
Oryza longistaminata , a wild species of African origin, has been reported to exhibit self-incompatibility (SI). However, the genetic pattern of its SI remained unknown. In this study, we conducted self-pollination and reciprocal cross-pollination experiments to verify that O. longistaminata is a strictly self-incompatible species. The staining of pollen with aniline blue following self-pollination revealed that although pollen could germinate on the stigma, the pollen tube was unable to enter the style to complete pollination, thereby resulting in gametophytic self-incompatibility (GSI). LpSDUF247 , a S -locus male determinant in the gametophytic SI system of perennial ryegrass, is predicted to encode a DUF247 protein. On the basic of chromosome alignment with LpSDUF247 , we identified OlSS1 and OlSS2 as Self-Incompatibility Stamen candidate genes in O. longistaminata . Chromosome segment analysis revealed that the Self-Incompatibility Pistil candidate gene of O. longistaminata ( OlSP ) is a polymorphic gene located in a region flanking OlSS1 . OlSS1 was expressed mainly in the stamens, whereas OlSS2 was expressed in both the stamens and pistils. OlSP was specifically highly expressed in the pistils, as revealed by RT-PCR and qRT-PCR analyses. Collectively, our observations indicate the occurrence of GSI in O. longistaminata and that this process is potentially controlled by OlSS1 , OlSS2 , and OlSP . These findings provide further insights into the genetic mechanisms underlying self-compatibility in plants.