Transformation of Arabidopsis with a Brassica SLG/SRK region and ARC1 gene is not sufficient to transfer the self-incompatibility phenotype

Abstract

Self-incompatibility (SI) promotes outbreeding in flowering plants, and in Brassica SI is genetically controlled by the S locus. Self-incompatible Brassica and self-fertile Arabidopsis belong to the same crucifer family. In addition, a comparative analysis reveals a high degree of microsynteny between the B. campestris S locus and its homologous region in Arabidopsis--with the notable exception that the Brassica SI genes, SLG and SRK, are missing. Brassica ARC1 encodes a component of the SRK signal transduction pathway leading to self-pollen rejection, and no closely related ARC1 homolog has been identified in Arabidopsis. The purpose of the research reported here was to introduce Brassica SI components into Arabidopsis in an attempt to compensate for the missing genes and to investigate whether the SI phenotype can be transferred. Inserts of approximately 40 kb from the fosmid clones F20 and F22, which span the B. napus W1 SLG-SRK region, were cloned into the plant transformation vector pBIBAC2. Transgenic plants were generated that expressed the Brassica SI genes in the flower buds. In addition, the endogenous, SLG-like, gene AtS1 was not co-suppressed by the Brassica SLG transgene. No SI phenotype was observed among the T1 BIBAC2-F20 and BIBAC2-F22 transgenic plants. When the ARC1 gene was transformed into BIBAC2-F20 or BIBAC2-F22 plants, the resulting BIBAC2-F20-ARC1 and BIBAC2-F22-ARC1 plants still set seeds normally, and no rejection response was observed when self-incompatible B. napus W1 pollen was placed on BIBAC2-F20-ARC1 or BIBAC2-F22-ARC1 Arabidopsis stigmas. Taken together, our results suggest that complementing Arabidopsis genome with Brassica SLG, SRK and ARC1 genes is unlikely to be sufficient to transfer the SI phenotype.

Recent Progresses on Self-incompatibility Research in Brassica Species

“…Actually, by using the genomic clone of the SLG/SRK region of Brassica species, A. thaliana was transformed. However, the transformants did not exhibit the SI phenotype (Bi et al 2000). In contrast, when A. thaliana was transformed with SRK and SCR derived from a closely related species, A. lyrata, the transformants partially exhibited a weak SI phenotype, suggesting that the downstream signaling cascade leading to the rejection of self-pollen is maintained in A. thaliana .…”

A proteomic analysis of plant programmed cell death

“…The protein identified in this study bears homology (40-60% similarity) to S-like glycoproteins and the S-like domain of receptor proteins kinases from several species, including Arabidopsis. Since Arabidopsis, like carrot, does not possess a genetic self-incompatibility system (Bi et al, 2000), the EP1-like protein may be involved in other receptor kinase activation pathways and signal transduction. The encoded EP1-like protein is predicted to be part of the secretory pathway (TargetP v1.01 (Emanuelsson et al, 2000); p < 0:05) and therefore may be secreted in Arabidopsis cell cultures undergoing PCD as part of a cell-to-cell signalling mechanism.…”

Signaling Events in Pollen Acceptance or Rejection in the Arabidopsis Species

“…thaliana is a self-compatible species that has lost its self-incompatibility system by the pseudogenization of the SCR/SP11 and SRK genes (Kusaba et al 2001 ;Bechsgaard et al 2006 ;Tang et al 2007 ;Shimizu et al 2008 ;Guo et al 2011 ). As A. thaliana is easily transformed, a number of studies have reintroduced the SCR/ SP11 or SRK genes from other Brassicaceae species in an attempt to reintroduce the self-incompatibility trait (Bi et al 2000 ;Nasrallah et al 2002 ). One approach was to transform SCR/SP11-SRK S-haplotypes from A. lyrata and C. grandifl ora into different A. thaliana ecotypes.…”