Different mechanisms generating sequence variability are revealed in distinct regions of the hydroxyproline-rich glycoprotein gene from maize and related specie*

Abstract

The sequences of the genes coding for a hydroxyproline-rich glycoprotein from two varieties of maize (Zea mays, Ac1503 and W22), a teosinte (Zea diploperennis) and sorghum (Sorghum vulgare) have been obtained and compared. Distinct patterns of variability have been observed along their sequences. The 500 bp region immediately upstream of the TATA box is highly conserved in the Zea species and contains stretches of sequences also found in the sorghum gene. Further upstream, significant rearrangements are observed, even between the two maize varieties. These observations allow definition of a 5' region, which is common to the four genes and is probably essential for their expression. The 3' end shows variability, mostly due to small duplications and single nucleotide substitutions. There is an intron present in this region showing a high degree of sequence conservation among the four genes analyzed. The coding region is the most divergent, but variability arises from duplications of fragments coding for similar protein blocks and from single nucleotide substitutions. These results indicate that a number of distinct mechanisms (probably point mutation, transposon insertion and excision, homologous recombination and unequal crossing-over) are active in the production of sequence variability in maize and related species. They are revealed in different parts of the gene, probably as the result of the different types of functional constraints acting on them, and of the specific nature of the sequence in each region.

Domain conservation in several volvocalean cell wall proteins

“…Homologous recombination and unequal crossing over have been proposed and examined as possible mechanisms for the generation of the repeated sequences that code for the conserved rod domain in higher plant extensins [ 15,36,45,59]. In addition, both the CELPs and the volvocalean wall proteins discussed here provide evidence for exon shuffling, whereby functional domains of various proteins are recombined to produce proteins with novel properties.…”

“…If this is the case, it should be possible to trace the evolutionary origin of all HRGPs to a small number of archetypal peptide domains. To date, however, most of the characterized genes and proteins derive from dicots, with the rest coming from monocots and gymnosperms, and there are few examples in the literature where multiple HRGPs have been examined from a single species [46] or from two species in the same genus [36]. An important resource for this kind of evolutionary approach is the green algae, which also produce cell wall HRGPs [58] and whose lineage within the phylum and the plant kingdom has been extensively analyzed [3,4,28,35].…”

Genetic, molecular and cellular approaches to the analysis of maize embryo development

“…A maize extensin protein (ZmHRGP) has been purified from maize cells and pericarp cell walls and its cDNA was cloned from a coleoptile library (Stiefel et al, 1988) and the homologous gene cloned and sequenced from different maize lines and closely related species such as teosinte (Stieffel et al, 1990;Raz et al, 1992), sorghum (Raz et al 1991) and rice (Caelles et al, 1992). The ZmHRGP protein was initially immunodetected in maize root tip cell walls of young maize seedlings .…”

Rapid changes induced in developmental programmes of the maize embryo detected by analysis of the expression of genes encoding proline‐rich proteins

“…Fragments from zmHyPRP [2] and zmHRGP [10] coding regions and H4 [11] coding and 3P non-translated regions were used as probes. …”