The participation of AtXPB1, the XPB/RAD25 homologue gene from Arabidopsis thaliana, in DNA repair and plant development

Abstract

SummaryNucleotide excision repair in Arabidopsis thaliana differs from other eukaryotes as it contains two paralogous copies of the corresponding XPB/RAD25 gene. In this work, the functional characterization of one copy, AtXPB1, is presented. The plant gene was able to partially complement the UV sensitivity of a yeast rad25 mutant strain, thus con®rming its involvement in nucleotide excision repair. The biological role of AtXPB1 protein in A. thaliana was further ascertained by obtaining a homozygous mutant plant containing the AtXPB1 genomic sequence interrupted by a T-DNA insertion. The 3¢ end of the mutant gene is disrupted, generating the expression of a truncated mRNA molecule. Despite the normal morphology, the mutant plants presented developmental delay, lower seed viability and a loss of germination synchrony. These plants also manifested increased sensitivity to continuous exposure to the alkylating agent MMS, thus suggesting inef®cient DNA damage removal. These results indicate that, although the duplication seems to be recent, the features described for the mutant plant imply some functional or timing expression divergence between the paralogous AtXPB genes. The AtXPB1 protein function in nucleotide excision repair is probably required for the removal of lesions during seed storage, germination and early plant development.

The Plant-Specific Kinase CDKF;1 Is Involved in Activating Phosphorylation of Cyclin-Dependent Kinase-Activating Kinases in Arabidopsis

“…XPD, in particular, has a role in CAK anchoring and stabilizes the complex through interaction with MAT1 (Reardon et al, 1996;Busso et al, 2000). In Arabidopsis, putative DNA helicases are also encoded in the genome (Ribeiro et al, 1998;Costa et al, 2001), but no homolog of MAT1 has been identified so far. This suggests that another factor(s) may participate in weak anchoring of CAK4At to TFIIH, which could allow dissociation of the 200-kD complex from TFIIH during our protein extraction and fractionation processes.…”

DNA repair-related genes in sugarcane expressed sequence tags (ESTs)

“…In Arabidopsis and tobacco plants, Ries et al (2000) have reported that the exposure of plants to elevated levels of ultraviolet (UV) solar radiation increases the frequency of somatic homologous DNA rearrangements, which affect genome integrity. The accumulation of DNA lesions in seeds seems to be involved in the seed aging process and lower germination rates (Vonarx et al, 1998;Costa et al, 2001). Therefore, the identification of mechanisms that avoid the accumulation of DNA damage in plants could lead to agriculturally useful improvements in various crops, including sugarcane.…”

Ultraviolet-Defense Mechanisms in Higher Plants

“…AtRAD1 and AtRAD2, which are homologs of human XPF and XPG nucleases, respectively, have been cloned from Arabidopsis by the analysis of UV-hypersensitive mutants uvh1 and uvh3, respectively (17,41,43). AtXPB1 and AtXPD, which are homologs of human DnA helicases essential for neR, have been characterized by the analysis of a UVhypersensitive mutant, uvh8, and a t-DnA insertion line, respectively (12,42). neR therefore is one of the important UV-defense mechanisms in plants.…”