RESUMEN
In plants, exposure to solar ultraviolet (UV) light is unavoidable, resulting in DNA damage. Damaged DNA causes mutations, replication arrest, and cell death, thus efficient repair of the damaged DNA is essential. A light-independent DNA repair pathway called nucleotide excision repair (NER) is conserved throughout evolution. For example, the damaged DNA-binding protein Radiation sensitive 4 (Rad4) in Saccharomyces cerevisiae is homologous to the mammalian NER protein Xeroderma Pigmentosum complementation group C (XPC). In this study, we examined the role of the Arabidopsis thaliana Rad4/XPC homologue (AtRAD4) in plant UV tolerance by generating overexpression lines. AtRAD4 overexpression, both with and without an N-terminal yellow fluorescent protein (YFP) tag, resulted in increased UV tolerance. YFP-RAD4 localized to the nucleus, and UV treatment did not alter this localization. We also used yeast two-hybrid analysis to examine the interaction of AtRAD4 with Arabidopsis RAD23 and found that RAD4 interacted with RAD23B as well as with the structurally similar protein HEMERA (HMR). In addition, we found that hmr and rad23 mutants exhibited increased UV sensitivity. Thus, our analysis suggests a role for RAD4 and RAD23/HMR in plant UV tolerance.
RESUMEN
Crenicichla chicha, new species, occurs in clear, fast-running waters with rocky substrates in the rio Papagaio and tributaries. It is distinguished from all other Crenicichla species by the combination of two character states: infraorbitals 3 and 4 co-ossified (vs. separated) and 66-75 scales in the row immediately above to that containing the lower lateral line (E1 row scales). Crenicichla chicha shares a smooth preopercular margin, co-ossification of infraorbitals 3 and 4, and some color features with C. hemera from the adjacent rio Aripuanã drainage, rio Madeira basin. It differs from Crenicichla hemera in more E1 scales (66-75 vs. 58-65) and presence of a conspicuous black narrow stripe running from infraorbital 3 obliquely caudoventrad toward the preopercular margin vs. a rounded and faint suborbital marking present on infraorbitals 3-4. Examination of the type series and additional material from the rio Aripuanã confirms that Crenicichla guentheri Ploeg, 1991 is a junior subjective synonym of C. hemera Kullander, 1990.
Crenicichla chicha, espécie nova, ocorre em águas claras, correntes e com substrato rochoso, no rio Papagaio e tributários. É distinta de todas as outras espécies de Crenicichla pela combinação de dois estados de caracteres: ossos infraorbitais 3 e 4 co-ossificados (vs. separados) e 66-75 escamas na série imediatamente superior àquela que contém a linha lateral posterior (série E1). Crenicichla chicha compartilha o pré-opérculo liso, a co-ossificação dos infraorbitais 3-4 e aspectos do colorido com Crenicichla hemera do rio Aripuanã, bacia do rio Madeira. Difere de C. hemera por possuir mais escamas na série E1 (66-75 vs. 58-65) e uma listra suborbital preta e estreita, bem evidente, percorrendo obliquamente desde o infraorbital 3 até a margem do pré-opérculo vs. uma mancha suborbital arredondada e fraca situada nos infraorbitais 3-4. O exame da série típica e de material adicional proveniente do rio Aripuanã confirma que C. guentheri Ploeg, 1991 é um sinônimo júnior de C. hemera Kullander, 1990.
