The S haplotype‐specific F‐box protein gene, SFB, is defective in self‐compatible haplotypes of Prunus avium and P. mume

Abstract

SummaryMany Prunus species, including sweet cherry and Japanese apricot, of the Rosaceae, display an S-RNase-based gametophytic self-incompatibility (GSI). The specificity of this outcrossing mechanism is determined by a minimum of two genes that are located in a multigene complex, termed the S locus, which controls the pistil and pollen specificities. SFB, a gene located in the S locus region, encodes an F-box protein that has appropriate S haplotype-specific variation to be the pollen determinant in the self-incompatibility reaction. This study characterizes SFBs of two self-compatible (SC) haplotypes, S 4¢ and S f , of Prunus. S 4¢ of sweet cherry is a pollen-part mutant (PPM) that was produced by X-ray irradiation, while S f of Japanese apricot is a naturally occurring SC haplotype that is considered to be a PPM. DNA sequence analysis revealed defects in both SFB 4¢and SFB f . A 4 bp deletion upstream from the HVa coding region of SFB 4¢ causes a frame-shift that produces transcripts of a defective SFB lacking the two hypervariable regions, HVa and HVb. Similarly, the presence of a 6.8 kbp insertion in the middle of the SFB f coding region leads to transcripts for a defective SFB lacking the C-terminal half that contains HVa and HVb. As all reported SFBs of functional S haplotypes encode intact SFB, the fact that the partial loss-of-function mutations in SFB are present in SC mutant haplotypes of Prunus provides additional evidence that SFB is the pollen S gene in GSI in Prunus.

Effects of converting natural forests to coniferous plantations on fruit and seed production and mating patterns in wild cherry trees

“…The magnitude of inbreeding depression is relatively high in outcrossing woody perennials (Duminil et al 2009). Most Prunus species predominantly outcross because of their gametophytic self-incompatibility that prevents self-fertilization (Ushijima et al 2004;Shuri et al 2012). The observed outcrossing rate (0.994 £ tm i £ 0.998) confirms the self-incompatibility in P. verecunda.…”

“…This species commonly occurs in broadleaf forests in the semimountainous ranges of central Japan. Most Prunus species have gametophytic self-incompatibility and predominantly reproduce by outcrossing (Ushijima et al 2004;Shuri et al 2012). Various animals, birds, bees, flies, and beetles, are the main pollinators of P. verecunda and are more abundant in natural forests than in coniferous plantations in central Japan (Taki et al 2013).…”

Identification and characterization of S-RNase genes and S-genotypes in Prunus and Malus species

“…More recently, two additional S-haplotypes have been reported (Hanada et al 2014). Whereas, over 20 S-haplotypes are reported in other Prunus species such as almond, sweet cherry, plum, apricot, and Japanese apricot (Ushijima et al 2003(Ushijima et al , 2004Yamane et al 2003a, b;Romero et al 2004;Vaughan et al 2006;Zhang et al 2007;Wu et al 2009Wu et al , 2013. In apple, S-haplotype profiling has been widely used in characterizing apple cultivars (Janssens et al 1995;Bokszczanin et al 2009;Kim et al 2009;Long et al 2010;Minamikawa et al 2010).…”

“…In Rosaceae, the pistil S-determinant is encoded by an S-RNase gene (Bo˘skovic´and Tobutt 1996;Sassa et al 1996;Ushijima et al 1998;Tao et al 1999), whereas, the S-haplotype-specific F-box [SFB]/S-locus F-box [SLF] is a candidate gene for the pollen S-determinant in Prunus species, belonging to the Prunoideae subfamily (Entani et al 2003;Ushijima et al 2003Ushijima et al , 2004Yamane et al 2003a;Zhang et al 2007). However, genes for the pollen S-determinant in Malus species, belonging to the Maloideae subfamily, have not been functionally characterized (Cheng et al 2006;Kakui et al 2007Kakui et al , 2011Okada et al 2008Okada et al , 2011Sassa et al 2007Sassa et al , 2010.…”

Characterization of X-ray-generated floral mutants carrying deletions at the S-locus of distylous Turnera subulata

“…Naturally occurring and induced S-locus mutants have proved to be a valuable resource in studies of homomorphic SI systems (Goring et al, 1993;Nasrallah et al, 1994;Sassa et al, 1997;Golz et al, 2000Golz et al, , 2001Ushijima et al, 2004;Sonneveld et al, 2005;Hauck et al, 2006). In heteromorphic SI systems, the genes determining distyly and tristyly have not yet been discovered (Barrett and Shore, 2008;Labonne et al, 2009).…”