Molecular characterisation of two novel maize LRR receptor-like kinases, which belong to the SERK gene family

Genes encoding two novel members of the leucine-rich repeat receptor-like k inase (LRR-RLK) superfamily have been isolated from maize (Zea mays L.). Th ese genes have been named ZmwSERK1 and ZmSERK1 since features such as a put ative leucine zipper (ZIP) and five leucine rich repeats in the extracellul ar domain, a proline-rich region (SPP) just upstream of the transmembrane d omain and a C-terminal extension (C) after the kinase domain identify them as members of the SERK (somatic embryogenesis receptor-like kinase) family. ZmSERK1 and ZmSERK2 are single-copy genes and show 79% identity among each other in their nucleotide sequences. They share a conserved intron/exon st ructure with other members of the SERK family. In the maize genome, ZmSERK1 maps to position 76.9 on chromosome arm 10L and ZmSERK2 to position 143.5 on chromosome arm 5L, in regions generally not involved in duplications. Zm SERK1 is preferentially expressed in male and female reproductive tissues w ith strongest expression in microspores. In contrast, ZmSERK2 expression is relatively uniform in all tissues investigated. Both genes are expressed i n embryogenic and non-embryogenic callus cultures.