Disruption of an RNA helicase/RNAse III gene in Arabidopsis causes unregulated cell division in floral meristems

Arabidopsis thaliana floral meristems are determinate structures that produ ce a defined number of organs, after which cell division ceases, A new rece ssive mutant, carpel factory (caf), converts the floral meristems to an ind eterminate state. They produce extra whorls of stamens, and an indefinite n umber of carpels. Thus, CAF appears to suppress cell division in floral mer istems, The function of CAF is partially redundant with the function of the CLAVATA (CLV) and SUPERMAN (SUP) genes, as caf clv and caf sup double muta nts show dramatically enhanced floral meristem over-proliferation. caf muta nt plants also show other defects, including absence of axillary infloresce nce meristems, and abnormally shaped leaves and floral organs. The CAF gene was cloned and found to encode a putative protein of 1909 amino acids cont aining an N-terminal DExH/DEAD-box type RNA helicase domain attached to a C -terminal RNaseIII-like domain. A very similar protein of unknown function is encoded by a fungal and an animal genome. Helicase proteins are involved in a number of processes, including specific mRNA localization and mRNA sp licing. RNase III proteins are involved in the processing of rRNA and some mRNA molecules. Thus CAF may act through some type of RNA processing event( s), CAF gives rise to two major transcripts of 2.5 and 6.2 kb, In situ hybr idization experiments show that CAF RNA is expressed throughout all shoot t issues.