Differential protein expression in compatible and incompatible pollen-pistil interactions in almond [Prunus dulcis (Miller) D. A. Webb] by 2D-DIGE and HPLC-MS/MS

Abstract

SummarySelf-incompatibility (SI) in almond [Prunus dulcis (Miller) D.A.Webb] is of the gametophytic-type and is controlled by the S-locus, which is highly polymorphic and includes two tightly-linked genes expressed in the pistil (as an SRNase) and in the pollen [as an S haplotype-specific F-box (SFB) protein]. Experimental evidence indicates that other proteins are also needed for the functioning of self-incompatibility. However, to date, S-RNase and SFB are the only components of the SI system identified in almond. Moreover, the cause(s) of a lack of S-RNase activity in selfcompatible almonds remain(s) unclear. This work aimed to identify the other proteins involved in the self- (in)compatible response in almond by comparative quantitative analysis of the differential expression of proteins following incompatible and compatible pollinations. Four self-incompatible almond cultivars were self-pollinated or cross-pollinated, and a homozygous self-compatible almond selection was self-pollinated. Proteins were extracted from the pollinated pistils and analysed by two-dimensional difference gel electrophoresis (2D-DIGE) and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Searches were performed against the NCBI database using the MASCOT and SEQUEST search engines and Proteome Discoverer v1.4 software. A total of 43 proteins, some with a key role in pollen-pistil interactions, were identified as being differentially expressed following incompatible or compatible pollination. These results provide the first profiles of differential protein expression during self-(in)compatibility in almond.