Minisymposium 12: Genome evolution

Abs # 25005: Comparative Analysis of the Receptor-Like Kinase Family in Arabidopsis thaliana and Rice

Presenter:	Shiu, Shin-Han , shiu@uchicago.edu
Authors	Shiu, Shin-Han  (A)   Karlowski, Wojciech M (B)   Pan, Runsun  (A) (D)  Tzeng, Yun-Huei  (C)   Mayer, Klaus F X (B)   Li, Wen-Hsiung  (A)
Affiliations:	(A): Dept. Ecol. & Evol., University of Chicago, USA (B): MIPS/IBI - National Research Center for Environment and Health, Germany (C): Dept. Mathematics, National Tsing Hua University, Taiwan (D): Inst. Information Sci., Academia Sinica, Taiwan

Receptor-like kinases (RLKs) belong to the large RLK/Pelle gene family, and it is known that the Arabidopsis genome contains more than 600 such members, which play important roles in plant growth, development and defense responses. Surprisingly, we found that rice has nearly twice as many RLK/Pelle members as Arabidopsis does and it is not simply a consequence of a larger predicted gene number in rice. From the inferred phylogeny of all Arabidopsis and rice RLK/Pelle members, we estimated that the common ancestor of Arabidopsis and rice had more than 440 RLK/Pelles and that large-scale expansions of certain RLK/Pelle members and fusions of novel domains have occurred in both the Arabidopsis and rice lineages since their divergence. In addition, the extracellular domains have higher non-synonymous substitution rates than the intracellular domains, consistent with the role of extracellular domains in sensing diverse signals. The lineage-specific expansions in Arabidopsis can be attributed to both tandem and large-scale duplications, whereas tandem duplication seems to be the major mechanism in recent expansions in rice. Interestingly, while the RLKs that are involved in development seem to have rarely been duplicated after the Arabidopsis-rice split, those that are involved in defense/disease resistance apparently have undergone many duplication events. These findings led us to hypothesize that most of the recent expansions of the RLK/Pelle family have involved defense/resistance-related genes.