Two Members of the Thioredoxin-h Family Interacts with the Kinase Domain of a Brassica S Locus Receptor Kinase

• Published in: The Plant cell Vol. 8; no. 9; pp. 1641 - 1650
• Main Authors: Bower, Michael S., Matias, Dinah D., Fernandes-Carvalho, Emily, Mazzurco, Maria, Gu, Tiesheng, Rothstein, Steven J., Goring, Daphne R.
• Format: Journal Article
• Language: English
• Published: American Society of Plant Physiologists 01.09.1996
• Subjects: Amino acids; Antibodies; Genetic loci; Insulin; Plant cells; Pollen; Proteins; Receptors; Thioredoxin; Yeasts
• ISSN: 1040-4651; 1532-298X
• DOI: 10.2307/3870256

To determine potential targets of the S locus receptor kinase (SRK) during the Brassica self-incompatibility response, a yeast two-hybrid library was screened with the SRK-910 protein kinase domain. Two thioredoxin-h-like clones, THL-1 and THL-2, were found to interact specifically with the SRK-910 protein kinase domain and not to interact with the protein kinase domains from the Arabidopsis receptor-like protein kinases (RLK) RLK4 and RLK5. The interaction between THL-1 and the SRK-910 protein kinase domain was confirmed using coimmunoprecipitation experiments with fusion proteins produced in Escherichia coli. THL-1 has thioredoxin activity based on an insulin reduction assay, and THL-1 is weakly phosphorylated by the SRK-910 protein kinase domain. THL-1 and THL-2 are both expressed in a variety of tissues but show some differences in steady state mRNA levels, with THL-2 being preferentially expressed in floral tissues. This indicates a more general biological function for these thioredoxins in addition to a potential role as effector molecules in the self-incompatibility signal cascade.