Defensive and secondary metabolism in Astragalus chrysochlorus cell cultures, in response to yeast extract stressor.

In this study it was aimed to investigate inducibility of secondary metabolism in Astragalus chrysochlorus by yeast extract which is known to cause the synthesis of defensive phenolic metabolites. Cell suspension cultures of Astragalus chrysochlorus responded to elicitor treatment (10 gl(-1) yeast extract) by increasing phenylalanine ammonia lyase (PAL E.C. 4.3.1.5) activity the key enzyme of phenylpropanoid pathway and accumulation of phenolic compounds. Yeast extract was added on 13th day in the cultures when cells were at early stage of logarithmic phase. The highest PAL activity (2.71 U microg protein(-1) min(-1)) was measured at 36 hr after addition of yeast extract and increasing of total phenolics accompanied with 221 microg g(-1) value as fresh weight (FW). Total phenolic content reached maximum value, 343.86 microg g(-1) FW, at 48 hr while control's value was 162 microg g(-1) FW. Maximum PAL activity and total phenolic content were 2.88 and 2.12 times higher than the controls of A. chrysochlorus cells, respectively. Our results indicate that there is a positive correlation between induced PAL activity and accumulation of total phenolics. It is considered that early defense response given to environmental stressors such as biotic and abiotic factors by upregulation of phenolic branch of secondary metabolism occurs in A. chrysochlorus with addition of yeast extract.