Genome-Wide Analysis of the RNase T2 Family and Identification of Interacting Proteins of Four ClS-RNase Genes in ‘XiangShui’ Lemon

Abstract

S-RNase plays vital roles in the process of self-incompatibility (SI) in Rutaceae plants. Data have shown that the rejection phenomenon during self-pollination is due to the degradation of pollen tube RNA by S-RNase. The cytoskeleton microfilaments of pollen tubes are destroyed, and other components cannot extend downwards from the stigma and, ultimately, cannot reach the ovary to complete fertilisation. In this study, four S-RNase gene sequences were identified from the ‘XiangShui’ lemon genome and ubiquitome. Sequence analysis revealed that the conserved RNase T2 domains within S-RNases in ‘XiangShui’ lemon are the same as those within other species. Expression pattern analysis revealed that S3-RNase and S4-RNase are specifically expressed in the pistils, and spatiotemporal expression analysis showed that the S3-RNase expression levels in the stigmas, styles and ovaries were significantly higher after self-pollination than after cross-pollination. Subcellular localisation analysis showed that the S1-RNase, S2-RNase, S3-RNase and S4-RNase were found to be expressed in the nucleus according to laser confocal microscopy. In addition, yeast two-hybrid (Y2H) assays showed that S3-RNase interacted with F-box, Bifunctional fucokinase/fucose pyrophosphorylase (FKGP), aspartic proteinase A1, RRP46, pectinesterase/pectinesterase inhibitor 51 (PME51), phospholipid:diacylglycerol acyltransferase 1 (PDAT1), gibberellin receptor GID1B, GDT1-like protein 4, putative invertase inhibitor, tRNA ligase, PAP15, PAE8, TIM14-2, PGIP1 and p24beta2. Moreover, S3-RNase interacted with TOPP4. Therefore, S3-RNase may play an important role in the SI of ‘XiangShui’ lemon.

The influence of the pollination compatibility type on the pistil S-RNase expression in European pear (Pyrus communis)

“…After semi-compatible pollination, the S-RNase expression in the upper region of the style also remained stable, though significantly higher compared to the other pollination types, followed by a delayed drop in expression at 3 dpp. Decreased S-RNase expression after cross-pollination and maintained expression after self-pollination have previously also been described in S. chacoense (O'Brien et al, 2002;Liu et al, 2009), lemon (Zhang et al, 2015;Li et al, 2022), and P. bretschneideri (Shi et al, 2017). Drawing upon these findings together with our own results in P. communis cv.…”

“…A decreased S-RNase expression after cross-pollination and higher expression after self-pollination was also found in lemon, a member of the Rutaceae family which was recently also found to harbor a similar type of S-RNase-dependent GSI ( Honsho, 2023 ). Expression analysis of the S3-RNase in lemon styles showed ten times higher expression after self-pollination compared to cross-pollination 20 h after pollination ( Li et al, 2022 ). In the Pyrus bretschneideri cultivar “Dangshan,” the expression of both S-RNase alleles ( Pb S 7 and Pb S 34 ) also decreased after cross-pollination and this occurred faster and more pronounced as compared to no pollination or self-pollination ( Shi et al, 2017 ).…”