The F-Box Protein AhSLF-S₂ Controls the Pollen Function of S-RNase–Based Self-Incompatibility

Abstract

Recently, we have provided evidence that the polymorphic self-incompatibility (S) locus-encoded F-box (SLF) protein AhSLF-S 2 plays a role in mediating a selective S-RNase destruction during the self-incompatible response in Antirrhinum hispanicum. To investigate its role further, we first transformed a transformation-competent artificial chromosome clone (TAC26) containing both AhSLF-S 2 and AhS 2 -RNase into a self-incompatible (SI) line of Petunia hybrida. Molecular analyses showed that both genes are correctly expressed in pollen and pistil in four independent transgenic lines of petunia. Pollination tests indicated that all four lines became self-compatible because of the specific loss of the pollen function of SI. This alteration was transmitted stably into the T1 progeny. We then transformed AhSLF-S 2 cDNA under the control of a tomato (Lycopersicon esculentum) pollen-specific promoter LAT52 into the self-incompatible petunia line. Molecular studies revealed that AhSLF-S 2 is specifically expressed in pollen of five independent transgenic plants. Pollination tests showed that they also had lost the pollen function of SI. Importantly, expression of endogenous SLF or SLF-like genes was not altered in these transgenic plants. These results phenocopy a well-known phenomenon called competitive interaction whereby the presence of two different pollen S alleles within pollen leads to the breakdown of the pollen function of SI in several solanaceaous species. Furthermore, we demonstrated that AhSLF-S 2 physically interacts with PhS 3 -RNase from the P. hybrida line used for transformation. Together with the recent demonstration of PiSLF as the pollen determinant in P. inflata, these results provide direct evidence that the polymorphic SLF including AhSLF-S 2 controls the pollen function of S-RNase-based self-incompatibility.

Protein Interactions in S-RNase-Based Gametophytic Self-Incompatibility

“…Analysis of progeny resulting from selfpollination demonstrated that all of the progeny inherited the transgene. Similar results were reported by Qiao et al (2004b) who transferred the Ah-SLF 2 gene of Antirrhinum hispanicum into S 3L S 3L Petunia hybrida. This experiment was conducted with two variations.…”

A Novel Nuclear-Localized CCCH-Type Zinc Finger Protein, OsDOS, Is Involved in Delaying Leaf Senescence in Rice

“…Genomic DNA isolation and Southern-blot analysis were performed as described previously (Qiao et al, 2004). DNA (5 mg) was digested, separated on 0.8% agarose gel, and transferred onto Hybond Nt (Amersham) membrane.…”

NaStEP: A Proteinase Inhibitor Essential to Self-Incompatibility and a Positive Regulator of HT-B Stability inNicotiana alataPollen Tubes

“…In vitro binding assays show that PiSLF in Petunia inflata physically interacts with S-RNases, although this interaction is stronger with nonself SRNases than with self S-RNases (Hua and Kao, 2006). Additional protein-protein interaction assays suggest that SLF/SFB may be a component of an SCF (for Skp1-Cullin1-F-box) or SCF-like complex (Qiao et al, 2004;Hua and Kao, 2006). Notably, data from Zhao et al (2010) in Petunia hybrida show that reduction of PhSSK1 (for P. hybrida SLF-interacting Skp-like1) and its Antirrhinum hispanicum ortholog, AhSSK1, is also required for cross-pollen compatibility.…”