Components of antioxidant system of Picrorhiza kurrooa exhibit different spatio-temporal behavior

Abstract

Antioxidant system is one of the important factors in regulating plant growth, development and adaptation. Thus, in order to have better insights into molecular mechanisms of growth and adaptation of a plant it is prerequisite to have known the status of various components of the antioxidant system of the plant. Here we studied the status of enzymatic and non-enzymatic components of the antioxidant system of picrorhiza (Picrorhiza kurrooa). Picrorhiza is an important medicinal herb of western Himalayan region and has been listed in the Red Data Book as an endangered species. Spatio-temporal analysis of ascorbic acid and glutathione in leaf, root and rhizome during different stages of development revealed differential status of these antioxidant molecules. Of the three tissues, ascorbic acid was found to be highest in leaves and lowest in roots. Interestingly, just opposite to that, glutathione was highest in roots and lowest in leaves. Using degenerate primers based approach followed by rapid amplification of complementary DNA (cDNA) ends method, full length cDNAs of three important genes namely Picrorhiza kurrooa ascorbate peroxidase (pkapx), Picrorhiza kurrooa monodehydroascorbate reductase (pkmdhar) and Picrorhiza kurrooa glutathione reductase (pkgr) of antioxidant system were cloned from picrorhiza. Complementary DNAs of pkapx, pkmdhar and pkgr contained 1,049, 2,016 and 1,664 bp, respectively. Expression analysis showed differential spatio-temporal expression of these genes. Expressions of all the three genes were found higher in roots as compared to rhizome and leaves. Temporal expression analysis of pkapx, pkmdhar and pkgr revealed differential transcript levels. Expression of pkapx exhibited negative correlation with the light intensity. Just opposite to the pkapx, expression pattern of pkgr revealed its positive correlation with light intensity. Expression pattern of pkmdhar revealed its light independent expression behavior. The findings may be useful to assess the role of cloned genes in picrorhiza growth, adaptation and can further be utilized for transgenic development for desired trait(s).