Isolation, characterization, and chromosomal location of a new cab gene from Arabidopsis thaliana

The Arabidopsis genes encoding the Chl a/b-binding protein of PSII Cab1, Cab2, and Cab3 have been isolated characterized. In as much as only three genes have been found, it is likely that there are more Arabidopsis cab genes, especially those of PSI, because these have been cloned in other species. The authors therefore attempted to clone PSI cab genes from Arabidopsis in an effort to understand the expression, regulation, structure, and function of higher plant Cab proteins. Taking advantage of the conservation of the PSI cab genes from several plant species, they designed two oligonucleotides as primers and used polymerase chain reaction to clone full-length cDNA clones from Arabidopsis. Data suggest that the complexity of PSI and PSII is, at least in part, a result of the complexity of the polypeptides in the thylakoid membrane. Even in Arabidopsis, there seem to be at least three forms of Cab proteins: PSI Cab, PSII Cab, and the smaller Cab-like Cab4.