Santos Isabel, Pires Helena, Almeida José M, Fidalgo Fernanda, Confraria Ana, Duarte Márcia, Borlido Júlio, Salema Roberto
Botany Department, School of Sciences, University of Porto, Rua do Campo Alegre, 1191, 4150-180 Porto, Portugal.
Institute for Molecular and Cellular Biology, University of Porto, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal.
Funct Plant Biol. 2006 Jul;33(7):639-651. doi: 10.1071/FP06024.
Plants contain multiple forms of catalase (CAT) and their specific functions remain uncertain. We cloned two potato cDNAs corresponding to CAT1 and CAT2 genes, analysed their phylogenetic relationship, and studied their expression and activity in different organs to gain clues to their functions. Phylogenetic trees and the alignment of CAT cDNA sequences provided evidence that CAT1 and CAT2 genes have high identity to catalases of other solanaceous species, but are not phylogenetically closely related to one another, which contradicts the phylogenetic closeness ascribed to these genes. Northern blot analyses revealed that expression of CAT genes is controlled by leaf developmental phase. CAT2 expression was higher in both very young and senescent leaves, whereas CAT1 mRNA accumulated mainly in mature leaf, where the lowest CAT2 expression occurred. CAT1 and CAT2 are also differentially expressed in root, sprout and petal. Expression and activity patterns are consistent with different physiological roles for CAT1 and CAT2 isoforms. CAT1 is considered to be associated with photorespiration whereas CAT2 would fulfill physiological roles unrelated to this process. CAT2 appears to be a multifunctional isoform, associated with glyoxysomal activity in leaf senescence, other processes in non-photosynthetic organs and defence, functions that in other solanaceous species are fulfilled by two different isoforms.
植物含有多种形式的过氧化氢酶（CAT），其具体功能尚不清楚。我们克隆了两个与CAT1和CAT2基因对应的马铃薯cDNA，分析了它们的系统发育关系，并研究了它们在不同器官中的表达和活性，以获取其功能线索。系统发育树和CAT cDNA序列比对提供了证据，表明CAT1和CAT2基因与其他茄科物种的过氧化氢酶具有高度同源性，但在系统发育上彼此并不密切相关，这与归因于这些基因的系统发育亲缘关系相矛盾。Northern印迹分析表明，CAT基因的表达受叶片发育阶段的控制。CAT2在非常幼嫩和衰老的叶片中表达均较高，而CAT1 mRNA主要在成熟叶片中积累，而成熟叶片中CAT2的表达最低。CAT1和CAT2在根、芽和花瓣中也有差异表达。表达和活性模式与CAT1和CAT2同工型的不同生理作用一致。CAT1被认为与光呼吸有关，而CAT2则履行与此过程无关的生理作用。CAT2似乎是一种多功能同工型，与叶片衰老中的乙醛酸循环体活性、非光合器官中的其他过程以及防御有关，这些功能在其他茄科物种中由两种不同的同工型来实现。
