Oxidative stress in Kalanchoe daigremontiana caused by Agrobacterium tumefaciens

Bakterija Agrobacterium tumefaciens upotrebljava se kao vektor za unos stranih gena u biljni genom odnosno stvaranje transgenih biljaka. Istraživanje interakcije između biljaka i ove bakterije znacajno je zbog poboljsanja ucinkovitosti transformacije biljnih stanica. Da bi se utvrdilo u kojoj mjeri ranjavanje biljke kao nužni preduvjet infekcije te infekcija biljnog tkiva bakterijom Agrobacterium tumefaciens uzrokuju oksidacijski stres određivani su pokazatelji oksidacijskog stresa u listovima biljke Kalanchoe daigremontiana na samom mjestu ranjavanja odnosno infekcije te u tkivu u neposrednoj blizini. Pokazatelji oksidacijskog stresa bili su aktivnost antioksidacijskih enzima pirogalol i gvajakol peroksidaze te katalaze, sastav njihovih izoenzima te kolicina vodikovog peroksida. U tumorskom tkivu utvrđen je porast aktivnosti enzima pirogalol i gvajakol peroksidaze tijekom tri tjedna. Također, uocena je i pojava novih izoenzima tih peroksidaza. U ozlijeđenom tkivu je samo pirogalol peroksidaza pokazala znacajno povisenu aktivnost tjedan dana nakon ranjavanja dok je u naredna dva tjedna njezina aktivnost bila na razini aktivnosti tog enzima u zdravom tkivu. Katalaza nije pokazala znacajnu razliku u aktivnosti između tumorskog i ostalog tkiva, a nije utvrđen ni povecan broj izoenzima. Kolicina vodikovog peroksida u zdravom i ozlijeđenom te tumorskom tkivu nije se znacajno razlikovala. U tkivu u neposrednoj blizini ozljeđivanja i infekcije nisu utvrđene znacajne promjene pokazatelja oksidacijskog stresa. Dobiveni rezultati ukazuju da infekcija bakterijom Agrobacterium tumefaciens ne uzrokuje izrazitiji oksidacijski stres u biljci Kalanchoe daigremontiana. Povecanje aktivnosti peroksidaze u ozlijeđenom i tumorskom tkivu može se povezati s ulogom tog enzima u procesima rasta koji dovode do zacijeljivanja ozljede odnosno rasta tumora na listu biljke. Agrobacterium tumefaciens can be used as a vector for transferring foreign genes into the plant genome as a way of creating transgenic plants. Studying interactions between plants and bacteria is significant for improving the efficiency of plant cell transformation. In order to determine to which extent plant wounding as a necessary requirement for infection as well as infection process by Agrobacterium tumefaciens itself are causing oxidative stress, parameters of oxidative stress was determined in leaves of Kalanchoe daigremontiana plant. Activity and isoenzyme pattern of antioxidant enzymes pyrogallol and guaiacol peroxidase and catalase as well as hydrogen peroxide content were measured in plant tissue at sites of infection and wounding as well as at the sites near them. In tumor tissue significant increase of pyrogallol and guaiacol peroxidase activity was observed during three weeks. Moreover, new isoenzymes appeared. In wounded tissue pyrogallol peroxidase showed significant increase in activity only during the first week after wounding. There was neither considerable difference in activity nor in isoenzyme pattern of catalase between tumor and other tissues. The hydrogen peroxide content was similar in healthy, tumor and wounded tissue. In tissues near the infection or wounding no significant changes that would indicate the presence of oxidative stress were noticed. Obtained results suggest that the infection of plant tissue by Agrobacterium tumefaciens did not cause prominent oxidative stress in Kalanchoe daigremontiana. Increase in peroxidase activity observed in wounded and tumor tissue could be connected with the role of peroxidase in growth processes during tissue regeneration and tumor growth.