Isolation of cDNAs encoding guanine nucleotide-binding protein β-subunit homologues from maize (ZGB1) and Arabidopsis (AGB1)

We have isolated cDNAs from maize (ZGB1) and Arabidopsis (AGB1) encoding proteins homologous to β subunits of guanine nucleotide-binding protein (G protein). The predicted ZGB1 and AGB1 gene products are 76% identical to each other and 41% or more identical to animal G protein β subunits. Both predicted proteins contain seven repeats of the so-called 'WD-40' motif, where WD is Trp-Asp. RNA blot analysis indicates that ZGB1 mRNA is present in the root, leaf, and tassel and that AGB1 mRNA is expressed in the root, leaf, and flower. DNA blot hybridizations indicate that maize and Arabidopsis genomes contain no other genes that are highly similar to ZGB1 and AGB1, respectively, suggesting that the newly isolated G protein β-subunit homologues are likely to have unique functions. Furthermore, these G protein β-subunit homologues are conserved among other plant species and may play important role(s) in plant signaling.