Molecular evolution of two actin genes from carrot

Abstract

We have isolated and sequenced two full-length cDNA clones encoding actin from carrot. The two carrot clones are almost identical at the nucleotide level, and are quite homologous to each other and to other plant actins at the amino acid level. In those regions where amino acid variation exists between the two genes from carrot, the differences have arisen from very simple changes at the nucleotide level. The most common changes are nucleotide insertion(s) coupled to the deletion of a different nucleotide(s) nearby in the DNA sequence, resulting in the restoration of the proper reading frame for the protein; thus, these changes can be viewed as multiple or coupled frameshift mutations. There are almost no base substitutions between the two carrot genes. In contrast to this, when the carrot actin nucleotide sequences are compared to those of a soybean actin gene or a maize actin gene, many base substitutions are observed (ca, 21.8% and 23.5%), more than half of which are third base changes which do not alter the protein sequence. At the amino acid level, both carrot genes show greater similarity to maize actin than they do to soybean actin, thus reinforcing the idea that plant actin genes diverged from a single common ancestral actin gene prior to the divergence of monocots and dicots.

The Cotton ACTIN1 Gene Is Functionally Expressed in Fibers and Participates in Fiber Elongation

“…A unique feature of the actin gene family is the position of introns that are conserved among actin genes in cotton and other plant species (Shah et al, 1983;Baird and Meagher, 1987;Nairn et al, 1988;Stranathan et al, 1989;McElroy et al, 1990;Meagher and Williamson, 1994;Cox et al, 1995;An et al, 1996). In Arabidopsis, actin genes have three small introns at identical locations as in GhACT genes except ACT2, in which the first intron between codons 20 and 21 is missing .…”

Molecular genetics of actin function

“…For example, rice actin 1 is more similar to Arabidopsis actin than any other rice actin [77]. The two carrot actins (dicot) are closer to maize (monocot) than to soybean (dicot) [78], suggesting that the formation of different actin gene families predated the divergence of monocots and dicots [55,56]. Especially when actins from different species are more similar than within a multigene family the possibility of isoform-specific functional differences must be considered.…”

Characterization of the rice (Oryza sativa) actin gene family

“…Therefore we propose that the name Act 1 be used for both the rice RAc 1 and the Arabidopsis thaliana AAcl sequences. A similar finding of close sequence similarity between a dicot and monocot actin protein has previously been reported for the deduced amino acid sequences of the carrot CAcl and maize MAcl actin genes [36]. In our sequence comparisons we were unable to discover the interspecific hierarchy of sequence identity in the rice actin gene family that had previously been reported for the soybean actin gene family [ 11 ].…”

“…Actin gene families in higher plants have been found to consist of at least six genes in soybean (Glycine max) [31,32], six genes in maize (Zea mays) [32], three genes in Arabidopsis thaliana [23], five genes in potato (Solanum tuberosum) [4], ten genes in tomato (Lycopersicon esculentum) [2] and two genes in carrot (Daucus carota) [36].…”