Molecular cloning and yeast two-hybrid provide new evidence for unique sporophytic self-incompatibility system of Corylus

The Corylus genus contains several important nut producing species and exhibits sporophytic self-incompatibility (SSI). However, the underlying molecular mechanisms of SSI in Corylus remain largely unknown. To clarify whether Corylus and Brassica share the same SSI molecular mechanism. We cloned ChaTHL1/2, ChaMLPK, ChaARC1, ChaEX70A1 genes from Ping'ou hybrid hazelnut using RACE techniques and tested the interaction between the ChaARC1 and ChaSRK1/2. We also examined the pistil-pollen interactions using scanning electron microscopy. We found no differences in the stigma surface within 1 h after compatible or incompatible pollination. Compatible pollen tubes penetrated the stigma surface, while incompatible pollen did not penetrate the stigma 4 h after pollination. Bioinformatics analysis revealed that ChaTHL1/2, ChaMLPK, ChaARC1 and ChaEX70A1 have corresponding functional domains. Quantitative real-time PCR (qRT-PCR) analysis showed that ChaTHL1/2, ChaMLPK, ChaARC1 and ChaEX70A1 were not regularly expressed in compatible or incompatible pollination. Furthermore, the expression patterns of ARC1, THL1/2, MLPK and Exo70A1 were quite distinct between Corylus and Brassica. According to yeast two-hybrid assays, ChaSRK1/2 did not interact with ChaARC1, confirming that the SRK-ARC1 signalling pathway implicated in the SSI response of Brassica was not conserved in Corylus. These results further reinforce the conclusion that, notwithstanding the similarity of the genetic basis, the SSI mechanism of Corylus does not conform in many respects with that of Brassica. Our findings could be helpful to better explore the potential mechanism of SSI system in Corylus.