Transcript level of hmgr gene and andrographolide accumulation in Andrographis paniculata grown under salinity treatment

Abstract

Andrographis paniculata (Hempedu Bumi) is among the famous medicinal plants, which has been used in treatment of various diseases worldwide since ancient times. A. paniculata is highly sought after and is being commercialized for its high value therapeutical compound, diterpene lactones (andrographolide). However, A. paniculata is sensitive to salinity stress, which is one of the major environmental problem that can severely supress plant growth and development as soluble salts accumulate in soil in high concentration. This study aims to measure the plant response and intensity of reactive oxygen species in A. paniculata subjected to saline condition. Generally, symptoms of salt toxicity were observed on morphology and physiology of A. paniculata including dehydration and browning of leaves. Histochemical staining of control and treated leaves showed that the accumulation of superoxide in salt-treated leaves was higher than the control, indicating oxidative stress. In addition, one of the genes involved in andrographolide biosynthesis is known as 3-hydroxy-3-methylglutaryl-coenzyme A reductase (hmgr). In this study, the transcript level of hmgr and andrographolide content in A. paniculata subjected to saline condition were examined using a qPCR and HPLC, respectively. The transcript level of hmgr gene in A. paniculata was not affected by salinity treatment. Similarly, the content of andrographolide remained unchanged despite gradual increment of salinity concentration. The results showed that although A. paniculata is a salt-sensitive plant, the tested salt concentration did not affect the transcript level of hmgr gene and andrographolide biosynthesis. This is particularly important, as it provides additional information on the effects of salt stress in A. paniculata including morpho-physiological characteristics, reactive oxygen species, hmgr transcript level and biosynthesis of andrographolide.