Exploring the Genetic Potential of Arundodonax L. as Hyperaccumulator of Heavy Metals

Abstract

Giant reed (A. donax) has previously been explored for physiological ability to accumulate and respond to various toxic metals like As, Cd, Cu, Cr, Zn, Pb etc. None of the investigations identified stress responding genes and associated proteins for the detoxification of these metals to understand the genetic basis of metal tolerance of A. donax as an established metallophyte. The current study aimed to explore the metals responsive genes of A. donax plants after exposure to various metals involved in metals uptake, accumulation, tolerance and detoxification.The plants were collected from uncontaminated sites and after propagation synthetic wastewater (25, 50, 75 and 100 mg-1L) of (Cr, Cd, As, Pb, Cu and Ni) was given for three weeks by using randomized block design (RBD) in hydroponics. After 10 days leaves were separated for genetic (GR, BHLH, YSL, CH, NRAMP and Amidase) protiomic (HSP70 and HO-1), antioxidants (SOD, POD, CAT) and MDA exploration along with physiological characteristics (heights, dry weight, chlorophyll analysis) were evaluated in response to metal stress. The metals uptake reduced dry weight, Chla, Chlb and total Chl contents of giant reed. The SOD, CAT, POD activities and MDA content increased significantly (p≤ 0.05) at the maximum metals concentration over control. The highest genes expression for carotenoid hydroxylase, glutathione reductase, YSL and amidase was observed in plants above 50mg/L concentration. However, differential bHLH gene expression and slightly increased gene expression of NRAMP was noted for different metals treatments. The phylogenic tree showed that giant reed genes were closely related to glutathione reductase gene, beta-carotene hydroxylase genes, transcription factor bHLH and putative amidase as found in wheat, maize, sorghum, bamboo and setaria. It is clear from the present research that the giant reed is not only a metals hyperaccumulator and hyper-tolerant plant but the presence of signaling transduction of HSP70 and HO-1 proteins might have contributed towards plant tolerance against metal stress. Giant reed has a hyperaccumulation ability based on its strong genetic battery which makes it suitable for phytoremediation purposes. These results provided insights into the mechanisms of A. donax tolerance and survival under heavy metals stress.