Panchuk Irina I, Zentgraf Ulrike, Volkov Roman A
Department of Biochemistry, National University of Chernivtsy, Kotsubinsky str. 2, 58012, Chernivtsy, Ukraine.
Planta. 2005 Nov;222(5):926-32. doi: 10.1007/s00425-005-0028-8. Epub 2005 Jul 21.
Oxygen-free radicals are thought to play an essential role in senescence. Therefore, the expression patterns of the small gene family encoding the H2O2 scavenging enzymes ascorbate peroxidase (APX; EC 1.11.1.11) were analyzed during senescence of Arabidopsis thaliana (L.) Heinh. Applying real-time RT-PCR, the mRNA levels were quantified for three cytosolic (APX1, APX2, APX6), two chloroplastic types (stromal sAPX, thylakoid tAPX), and three microsomal (APX3, APX4, APX5) isoforms identified in the genome of Arabidopsis. The genes of chloroplastic thylakoid-bound tAPX and the microsomal APX4 exhibit a strong age-related decrease of mRNA level in leaves derived from one rosette as well as in leaves derived from plants of different ages. In contrast to the tAPX, the mRNA of sAPX was only reduced in old leaves of old plants. The microsomal APX3 and APX5, and the cytosolic APX1, APX2, and APX6 did not show remarkable age-related changes in mRNA levels. The data show that expression of the individual APX genes is differentially regulated during senescence indicating possible functional specialization of respective isoenzymes. The hydrogen peroxide levels seem to be controlled very precisely in different cell compartments during plant development.
人们认为氧自由基在衰老过程中起着至关重要的作用。因此，在拟南芥衰老过程中，对编码过氧化氢清除酶抗坏血酸过氧化物酶（APX；EC 1.11.1.11）的小基因家族的表达模式进行了分析。应用实时逆转录聚合酶链反应，对拟南芥基因组中鉴定出的三种胞质同工型（APX1、APX2、APX6）、两种叶绿体同工型（基质sAPX、类囊体tAPX）和三种微粒体同工型（APX3、APX4、APX5）的mRNA水平进行了定量。叶绿体类囊体结合的tAPX基因和微粒体APX4基因在莲座叶以及不同年龄植株的叶片中，mRNA水平均呈现出与衰老相关的显著下降。与tAPX不同，sAPX的mRNA仅在老龄植株的老叶中减少。微粒体APX3和APX5以及胞质APX1、APX2和APX6的mRNA水平在衰老过程中未表现出明显的与年龄相关的变化。数据表明，在衰老过程中，各个APX基因的表达受到不同的调控，这表明相应同工酶可能具有功能特异性。在植物发育过程中，过氧化氢水平似乎在不同细胞区室中受到非常精确的控制。
