Distinct Self-recognition in the <i>Prunus</i> S-RNase-based Gametophytic Self-incompatibility System

Abstract

Prunus fruit tree species exhibit S-ribonuclease (S-RNase)-based gametophytic self-incompatibility (GSI). This system is also present in the families Plantaginaceae and Solanaceae and the tribe Maleae of the family Rosaceae. In S-RNase-based GSI, self/nonself-recognition between the pistil and pollen is controlled by the pistil S determinant S-ribonuclease gene (S-RNase) and the pollen S determinant F-box gene(s). Accumulated evidence indicates the Prunus pollen S locus contains a single F-box gene, while that of other plants consists of multiple F-box genes. The pollen S F-box genes are called S haplotype-specific F-box (SFB), S-locus F-box brothers (SFBB), and S-locus F-box (SLF) in Prunus, Maleae, and Solanaceae species, respectively. The consequences of pollen S gene mutations and heterodiallelic pollen production differ between Prunus species and other plants, suggesting there are different pollen S functions during self/nonself-recognition. The GSI systems of Prunus and other plants are believed to include the ubiquitin proteasome system for protein degradation. However, Prunus SFB is assumed to facilitate the S-RNase cytotoxic effects during selfrecognition, while SLFs and SFBBs are thought to function collaboratively during nonself-recognition to avoid S-RNase cytotoxicity. This review summarizes the distinct features of the S-RNase-based GSI mechanism in Prunus species, with special references to the recent advances in our understanding of S-RNase-based GSI.

Isolation and Characterization of <i>S-RNase</i>-homologous Genes Expressed in Styles in ‘Hyuganatsu’ (<i>Citrus tamurana</i> hort. ex Tanaka)

“…Additionally, the DeepLoc program predicted that all the proteins are likely to be soluble and localized in the extracellular space (Table 4). This is also a common feature of S-RNases (Anderson et al, 1989;Certal et al, 1999) and is thought to be associated with the nature of the interaction between S-RNase and pollen (Matsumoto and Tao, 2016), suggesting that CtRNS genes are correlated with SI in Citrus.…”

“…However, the key genes that determine S haplotypes and function in self/non-self recognition have not yet been identified. Among GSI plant species, the Rosaceae, Solanaceae, and Plantaginaceae families share the same SI system and the molecular mechanisms regulating this process have been better characterized (Matsumoto and Tao, 2016;Tao and Iezzoni, 2010). The SI system in these families is ruled by two different closely linked genes that define the pistil and pollen S specificities.…”

The evolutionary history of plant T2/S-type ribonucleases

“…A number of details remain murky, as these models are highly preliminary and, for example, a general inhibitor necessary for coherence of the proposed self-recognition Prunus model remains unidentified. Nevertheless, these differences appear fairly profound, because we lack a sound theory to explain how minor background mutations could switch between a mechanism with non-self-recognition that inhibits S-RNase cytotoxicity to one in which self-recognition elicits S-RNase cytotoxicity, for each of several dozen segregating alleles ( Matsumoto & Tao, 2016 ).…”

Peer Review #1 of "Shot-gun proteome and transcriptome mapping of the jujube floral organ and identification of a pollen-specific S-locus F-box gene (v0.1)"

“…5), in which GSI exhibited a distinct system of recognition between pollen and pistil involving a single SFB gene. This contrasts with multiple F-box genes that are activated in other plants (Matsumoto and Tao 2016). With the formerly identified S-RNase gene in Z. jujuba, therefore, we concluded that Jujube GSI behaviour was like Prunus and controlled by the S-RNase and a single SFB gene together.…”