Effects of salt stress on Opuntia streptacantha Lem. species

Abstract

Salinitet je jedan od glavnih čimbenika koji ograničavaju biljni razvoj i produktivnost, posebno važnih usjeva. U pustinjskim i polupustinjskim područjima, zbog nedostatka pitke vode, povećana je upotreba slane vode za navodnjavanje u poljoprivredi. U uvjetima solnog stresa i nedostatka vode, Pro je jedan od osmolita koji se najviše nakuplja u biljkama, stoga se mjerio sadržaj Pro u uvjetima solnog stresa. Ispitivana je ekspresija Δ1-pirolin-5-karboksilat sintetaze (gen Osp5cs) te aktivnost P5CS (γ-glutamil kinaza i glutamat-5-semialdehid dehidrogenaza) kao glavnog enzima biosintetskog puta Pro kod vrste O. streptacantha Lem. Mlade biljke O. streptacantha Lem. su nakon tretmana solnim stresom (6, 9 i 11 dana), pokazale smanjenje debljine kladodija i duljine korijena te značajno i postepeno nakupljanje Pro u ovisnosti o koncentraciji i vremenu. Solni je stres, općenito, doveo do smanjenja aktivnosti P5CS (γ-glutamil kinaza), osim pri koncentraciji NaCl-a od 75 i 150 mM tijekom šestog dana. Gen Osp5cs vrste O. streptacantha Lem. je induciran solnim stresom devetog i jedanaestog dana tretmana, što je potvrđeno RT-PCR analizom. U mladim je kladodijima ABA, isto tako, inducirala ekspresiju gena Osp5cs. Pod utjecajem solnog stresa postoji jasna povezanost između nakupljanja Pro i transkripcijske regulacije gena Osp5cs, što se ne poklapa s promjenama u aktivnosti enzima P5CS. Pro bi mogao djelovati kao osmolit u uvjetima solnog stresa te imati uloge u osmotskoj regulaciji i zaštiti fotosintetske aktivnosti O. streptacantha Lem.Salinity is one of the major factors limiting plant development and productivity, mainly of important crops. In arid and semiarid regions due to fresh water shortage, agriculture has increased usage of saline water. In salt stress and water deficit conditions, Pro is one of the most accumulated osmolytes in plants thus Pro content has been measured in such conditons. Expression level of Δ1-pyrroline-5-carboxylate synthetase (Osp5cs gene) and P5CS (γ-glutamyl kinase and glutamate-5-semialdehyde dehydrogenase) as a major enzyme of Pro biosynthetic pathway has been measured in O. streptacantha Lem. Salt stress treatment (6, 9 and 11 days) of O. streptacantha Lem. young plants resulted in a decrease of cladode thickness and root lenght, and in a significant and gradual accumulation of Pro depending of time and concentration. In general, salt stress has lead to P5CS (γ-glutamyl kinase) reduced activity, except at 75 and 150 mM NaCl at the sixth day. Osp5cs gene of O. streptacantha Lem. was induced by salt stress at ninth and eleventh day of treatment which has been confirmed by RT-PCR analysis. ABA also induced Osp5cs gene expression in young cladodes. Pro accumulation and Osp5cs gene transcription regulation revealed evident correlation between them under salt stress conditions without conferring with the changes in P5CS enzymatic activity. Pro might function as an osmolyte in salt stress conditons and might have a major role in osmotic regulation and photosyntetic activity protection of O. streptacantha Lem