Dear Mhd

You need data to answer your question. The first thing I would do is the measure the internal ABA content and then measure the activity of ROS scavenging enzymes such as catalase and peroxidases. The main sources of peroxide are photorespiration and superoxide dismutase. The other thing is that the redox status of the plant should be considered based on numerous aspects. In other words: is your mutant more tolerant to oxidative stress as a whole than the wild type. I mean if the mutant does not accumulate peroxide, does it do the same for superoxide?

In case your mutant has higher ROS scavenging activities, is it because of increased activity per se or due to increased non enzymatic antioxidants pool such as ascorbate or phenols?

It has been demonstrated that OsAPX gene expression and H2O2 production were increased in response to NaCl in roots of etiolated rice seedlings (Tsai et al. 2004, 2005). However, OsAPX8 expression and APX activity induced by NaCl are not mediated through H2O2 in rice roots (Tsai et al. 2005; Hong et al. 2007). In rice roots, accumulation of ABA in response to NaCl was correlated with upregulation of OsAPX8 expression (Hong et al. 2007). Moreover, exogenous application of ABA also specifically enhanced the expression of OsAPX8. Similarly, application of ABA increased the expression of APX genes in pea, rice, and sweet potato (Mittler and Zilinskas 1992; Agrawal et al. 2003; Park et al. 2004). These findings indicate that NaCl induced expression of APX is mediated through an accumulation of the ABA.

Another great challenge is how to apply the knowledge obtained

to improve the environmental stress tolerance of crops,

a potentially significant benefit of this research. Classical genetics

suggests that plant abiotic stress tolerance is controlled by

multiple loci, each contributing a minor effect (minor genes);

therefore, the manipulation of a master regulatory gene

through biotechnology is considered to be more efficient than

conventional breeding strategies in which it is difficult to break

negative linkage for many loci at one time. Nevertheless, large

gaps remain between basic research and the production of

stress-tolerant crops. First, the standard assays, including screening

criteria and methods, are different between Arabidopsis and

crop species. Proper assessments of environmental stress tolerance

for crops need to be established according to the actual

requirements of agricultural production.

DELLA proteins are also able to promote the expression of

genes encoding reactive oxygen species (ROS)-detoxifying enzymes

to reduce ROS levels in cells after biotic or abiotic attack,

thereby delaying cell death and enhancing tolerance (Achard

et al. 2008b).

In case your mutant has higher ROS scavenging activities, is it because of increased activity per se or due to increased non enzymatic antioxidants pool such as ascorbate or phenolics in general? What about DPPH, IC50, Non- photosynthetic activity, ARE?