Plants are continuously exposed to agents that can generate DNA lesions. Nucleotide Excision Repair (NER) is one of the repair pathways employed by plants to protect their genome, including from sunlight. The Xeroderma Pigmentosum type B (XPB) protein is a DNA helicase shown to be involved in NER and is also an essential subunit of the Transcription Factor IIH (TFIIH) complex. XPB was found to be a single copy gene in eukaryotes, but found as a tandem duplication in the plant Arabidopsis thaliana, AtXPB1 and AtXPB2. We aimed to investigate whether the XPB in tandem duplication was common within members of the Brassicaceae. We analyzed genomic DNA of species from different tribes of the family and the results indicate that the tandem duplication occurred in Camelineae tribe ancestor, of which A. thaliana belongs, at approximately 8 million years ago. Further experiments were devised to study possible functional roles for the A. thaliana AtXPB paralogs. A non-coincident expression profile of the paralogs was observed in various plant organs, developmental and cell cycle stages. AtXPB2 expression was observed in proliferating cells and clustered with the transcription of other components of the TFIIH such as p44, p52 and XPD/UVH6 along the cell cycle. AtXPB1 gene transcription, on the other hand, was enhanced specifically after UV-B irradiation in leaf trichomes. Altogether, our results reported herein suggest a functional specialization for the AtXPB paralogs: while the AtXPB2 paralog may have a role in cell proliferation and repair as XPB of other eukaryotes, the AtXPB1 paralog is most likely implicated in repair functions in highly specialized A. thaliana cells.

植物不断暴露于可能产生DNA损伤的物质中。核苷酸切除修复（NER）是植物用来保护其基因组（包括免受阳光照射）的修复途径之一。X型皮肤干燥色素B（XPB）蛋白是一种DNA解旋酶，显示与NER相关，并且还是转录因子IIH（TFIIH）复合物的必需亚基。XPB被发现是真核生物中的单拷贝基因，但在植物拟南芥，AtXPB1和AtXPB2中发现为串联复制。我们旨在调查XPB是否十字花科在十字花科中很常见。我们分析了该家族不同部落物种的基因组DNA，结果表明串联复制发生在大约800万年前的拟南芥所属的Camelineae部落祖先中。设计了进一步的实验来研究拟南芥AtXPB旁系同源物的可能功能。在各种植物器官，发育和细胞周期阶段观察到旁系同源物的非一致表达谱。在增殖细胞中观察到AtXPB2表达，并与TFIIH的其他成分（例如p44，p52和XPD / UVH6）的转录聚集在一起沿着细胞周期。另一方面，在叶片毛状体中进行UV-B照射后，AtXPB1基因的转录特别增强。总的来说，本文报道的结果表明AtXPB旁系同源物的功能专一性：尽管AtXPB2旁系同源物可能像其他真核生物的XPB一样在细胞增殖和修复中起作用，但AtXPB1旁系同源物很可能与高度特化拟南芥的修复功能有关。细胞。