MOLECULAR CHARACTERIZATION OF A NEW-TYPE OF RECEPTOR-LIKE KINASE (WLRK) GENE FAMILY IN WHEAT

In plants, several types of receptor-like kinases (RLK) have been isol ated and characterized based on the sequence of their extracellular do mains. Some of these RLKs have been demonstrated to be involved in pla nt development or in the reaction to environmental signals. Here, we d escribe a RLK gene family in wheat (wlrk, wheat leaf rust kinase) with a new type of extracellular domain. A member of this new gene family has previously been shown to cosegregate with the leaf rust resistance gene Lr10. The diversity of the wlrk gene family was studied by cloni ng the extracellular domain of different members of the family. Sequen ce comparisons demonstrated that the extracellular domain consists of three very conserved regions interrupted by three variable regions. Li nkage analysis indicated that the wlrk genes are specifically located on chromosome group 1 in wheat and on the corresponding chromosomes of other members of the Triticeae family. The wlrk genes are constitutiv ely expressed in the aerial parts of the plant whereas no expression w as detected in roots. Protein immunoblots demonstrated that the WLRK p rotein coded by the Lrk10 gene is an intrinsic plasma membrane protein . This is consistent with the hypothesis that WLRK proteins are recept or protein kinases localized to the cell surface. In addition, we pres ent preliminary evidence that other disease resistance loci in wheat c ontain genes which are related to wlrk.