Structural basis for specific self-incompatibility response in Brassica

Rui Ma, Zhifu Han, Zehan Hu, Guangzhong Lin, Xinqi Gong, Heqiao Zhang, June B. Nasrallah, Jijie Chai

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


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 extracellular 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.

Original languageEnglish (US)
Pages (from-to)1320-1329
Number of pages10
JournalCell Research
Issue number12
StatePublished - Dec 1 2016
Externally publishedYes


  • Brassica
  • Crystal structure
  • Homodimerization
  • Receptor kinase
  • S-domain
  • SRK-SCR complex
  • Self-incompatibility

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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