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S‐protein mutants indicate a functional role for SBP in the self‐incompatibility reaction of Papaver rhoeas
Author(s) -
Jordan Nicholas D.,
Kakeda Katsuyuki,
Conner Alex,
Ride Jon P.,
FranklinTong Verica E.,
Franklin F. Christopher H.
Publication year - 1999
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1999.00585.x
Subject(s) - pollen , mutant , papaver , biology , biochemistry , genetics , gene , botany
Summary The self‐incompatibility response involves S ‐allele specific recognition between stigmatic S proteins and incompatible pollen, resulting in S‐specific pollen inhibition. In Papaver rhoeas , the pollen S gene product is predicted to be a receptor that interacts with the stigmatic S protein in an S specific manner. We recently identified an S protein binding protein (SBP) in pollen that binds stigmatic S proteins, although apparently not in an S ‐allele‐specific manner. In order to investigate the functional significance of the interaction between S proteins and SBP, we constructed mutant derivatives of the S 1 protein and tested their SBP‐binding activity and their biological activity. Here we present an evaluation of nine mutant derivatives of the S 1 protein. Western ligand blotting was used to show that mutations to amino acid residues in predicted loops 2 and 6 of the S 1 protein cause significant reductions in their SBP‐binding activity. These same mutants show a concomitant reduction in their ability to inhibit incompatible pollen. This establishes a direct link between SBP binding and inhibition of incompatible pollen and implicates SBP as a pollen component playing a key role in the self‐incompatibility reaction. We discuss the possible nature of the contribution of SBP in the S‐specific rejection of incompatible pollen.