환경 스트레스에 의해 야기되는 활성 산소종에 의한 피해에 내성을 가지는 식물의 개발을 위하여 딸기 유래의 cytosolic ascorbate peroxidase 유전자(ApxSC7)를 Agrobacterium tume-faciens LBA4404를 매개로 형질전환 시켰다. Hygromycin으로 선발된 캘러스로부터 재분화 된 식물체는 야생형과 비교하여 형태적으로 차이를 나타내지 않았다. PCR 및 Southern blot 분석을 통하여 형질전환 식물체의

A cytosolic ascorbate peroxidase, hydrogen peroxide-scavenging enzyme, was characterized from Codonopsis lanceolata. The cytosolic ascorbate peroxidase cDNA (CAPX) was 983 nucleotides long and possess an open reading frame of 753 bp with 251 amino acids (MW 27.9 kDa) with pI 5.61. The deduced amino acid sequence of CAPX shows high homology to other known cytosolic APXs (78~83%), but the CAPX was clustered independently from compared ten plant APXs. The CAPX gene was highly expressed in leaf and stem tissues, but not in root. When Codonopsis leaves cut using scalpel were soaked in 1 mM hydorgen peroxide, the expression of CAPX gene was suppressed.

Ascorbate peroxidase (APX) plays a crucial role in the detoxification of hydrogen peroxide. APX activity is maintained significantly higher in the paraquat­treated leaves of the paraquat-tolerant Rehmannia glutinos. This study was conducted to understand structural and regulatory characteristics of APX gene in R. glutinosa. A putative APX cDNA clone (RgAPX1) was isolated from a leaf cDNA library using a partially sequenced expressed sequence tag clone. RgAPX1 is consisted of 1148 bp nucleotides and contains an open reading frame encoding a 250 amino acid-long polypeptide. Deduced RgAPX1 amino acid sequence shares higher sequence similarity to cytosolic APXs. RgAPX1. expression was higher in the leaf than in the flower and root. Southern blot result indicates the presence of one or two RgAPX1-related genes in R. glutinosa genome. RgAPX1 transcription was affected differentially by various stresses and phytohormone. The results indicate that RgAPXl is constitutively expressed in most tissues and its expression is modulated for the immediate and efficient detoxification of H2O2 under normal and stress conditions.

To assess resistance of transgenic tobacco plants which overexpress superoxide dismutase (SOD) and ascorbate peroxidase (APX) in chloroplasts to water stress, changes in leaf water potential, turgor potential, stomatal conductance and transpiration rate were measured. Leaf water potential in all plants remained high up to day 4 after withholding water but thereafter decreased markedly. In spite of a remarkable decrease in leaf water potential, some of transgenic plants maintained higher turgor potential compared with control plant on day 12. In particular, the transgenic plant expressing MnSOD showed an outstanding maintenance in turgor pressure by osmotic adjustment throughout the experiment, resulting in high stomatal conductance and transpiration rate. However, among transgenic plants, osmotic potential was reduced more effectively in multiple transformants such as the double transformant expressing both MnSOD and APX, and the triple transformant expressing CuznSOD, MnSOD and APX than single transformants. Consequently, further research is needed to get general agreement on the tolerance of transgenic plants to water stress at different growth stages for each transgenic plant.