Structural basis for specific self-incompatibility response in Brassica

Self-incompatibility （SI） is a widespread mechanism in flowering plants which prevents self-fertilization and inbreeding. In Brassica, recognition of the highly polymorphic S-locus cysteine-rich protein （SCR; or S-locus protein 11） by the similarly polymorphic S-locus receptor kinase （SRK） dictates...

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Published inCell research Vol. 26; no. 12; pp. 1320 - 1329
Main Authors Ma, Rui, Han, Zhifu, Hu, Zehan, Lin, Guangzhong, Gong, Xinqi, Zhang, Heqiao, Nasrallah, June B, Chai, Jijie
Format Journal Article
LanguageEnglish
Published England Nature Publishing Group 01.12.2016
Subjects
Amino Acid Sequence
Binding
Brassica
Brassica - metabolism
Crystal structure
Crystallography, X-Ray
Dimerization
Fertilization
Flowering
Inbreeding
Incompatibility
Loci
Monomers
Mutagenesis
Mutation
Original
Plant Proteins - chemistry
Plant Proteins - genetics
Plant Proteins - metabolism
Plants (botany)
Protein Binding
Protein Kinases - chemistry
Protein Kinases - genetics
Protein Kinases - metabolism
Protein Structure, Quaternary
Protein Structure, Tertiary
Proteins
Self-fertilization
Self-incompatibility
Sequence Alignment
Shape recognition
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Summary:Self-incompatibility （SI） is a widespread mechanism in flowering plants which prevents self-fertilization and inbreeding. In Brassica, recognition of the highly polymorphic S-locus cysteine-rich protein （SCR; or S-locus protein 11） by the similarly polymorphic S-locus receptor kinase （SRK） dictates the SI specificity. Here, we report the crystal structure of the extraceilular domain of SRK9 （eSRK9） in complex with SCR9 from Brassica rapa. SCR9 binding induces eSRK9 homodimerization, forming a 2：2 eSRK：SCR heterotetramer with a shape like the letter ＂A＂. Specific recognition of SCR9 is mediated through three hyper-variable （hv） regions of eSRK9. Each SCR9 simultaneously interacts with hvI and one-half of hvII from one eSRK9 monomer and the other half of hvII from the second eSRK9 monomer, playing a major role in mediating SRK9 homodimerization without involving interaction between the two SCR9 molecules. Single mutations of residues critical for the eSRK9-SCR9 interaction disrupt their binding in vitro. Our study rationalizes a body of data on specific recognition of SCR by SRK and provides a structural template for understanding the co-evolution between SRK and SCR.
Bibliography:Self-incompatibility （SI） is a widespread mechanism in flowering plants which prevents self-fertilization and inbreeding. In Brassica, recognition of the highly polymorphic S-locus cysteine-rich protein （SCR; or S-locus protein 11） by the similarly polymorphic S-locus receptor kinase （SRK） dictates the SI specificity. Here, we report the crystal structure of the extraceilular domain of SRK9 （eSRK9） in complex with SCR9 from Brassica rapa. SCR9 binding induces eSRK9 homodimerization, forming a 2：2 eSRK：SCR heterotetramer with a shape like the letter ＂A＂. Specific recognition of SCR9 is mediated through three hyper-variable （hv） regions of eSRK9. Each SCR9 simultaneously interacts with hvI and one-half of hvII from one eSRK9 monomer and the other half of hvII from the second eSRK9 monomer, playing a major role in mediating SRK9 homodimerization without involving interaction between the two SCR9 molecules. Single mutations of residues critical for the eSRK9-SCR9 interaction disrupt their binding in vitro. Our study rationalizes a body of data on specific recognition of SCR by SRK and provides a structural template for understanding the co-evolution between SRK and SCR.
31-1568
self-incompatibility; Brassica; receptor kinase; homodimerization; SRK-SCR complex; S-domain; crystal structure
ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ISSN:1001-0602
1748-7838
DOI:10.1038/cr.2016.129