DUF538 protein superfamily is predicted to be chlorophyll hydrolyzing enzymes in plants

Abstract

The possible hydrolytic activity towards chlorophyll molecules was predicted for DUF538 protein superfamily in plants. It was examined by using computational as well as experimental tools including in vitro chlorophyll degradation, antioxidant compounds production and in vivo real-time gene expression tests.Comparison of the computational data with the experimental results indicated that DUF538 proteins might be chlorophyll hydrolyzing enzyme (most probably carboxyesterase) which degrade chlorophyll molecules (66 % per 12 hrs) to produce new compounds (1.8 fold per 12 hrs) with antioxidant properties. The relevance of DUF538 gene expression level with the chlorophyll contents (2.8 fold increase per chlorophyll content of 50 %) of the drought-stressed leaves showed that chlorophyll degradation by DUF538 is most probably induced in response to stress stimuli. Despite membranous chlorophyll catabolic pathways, DUF538-dependent reactions is predicted to be occurred in the cytosol of the under stressed plants. We addressed as to whether chlorophyll breakdown to antioxidant compounds by DUF538 is a defense mechanism of plants against stress stimuli, in vivo? This question is going to be investigated in our next research project.

Characterization and Functional Divergence of a Novel DUF668 Gene Family in Rice Based on Comprehensive Expression Patterns

“…Moreover, the DUF283 domain of Dicer proteins was required for siRNA processing in gene silence [5,6]. The DUF538 superfamily was predicted to perform hydrolytic activity towards chlorophyll molecules [7,8]. In addition, the amaranth abiotic stress-induced gene (AhDGR2) encodes a DUF642 protein involved in salt and abscisic acid (ABA) hyper-sensibility in Arabidopsis [9].…”

Cell Wall Proteome of Wheat Grain Endosperm and Outer Layers at Two Key Stages of Early Development

“…As in wheat, several DUF538 were identified in the developing grain of B. distachyon [25]. Several functions have been suggested for proteins containing this domain of yet unknown function, such as their involvement in the photosynthetic system of plants by degrading chlorophyll molecules to antioxidant compounds under stress induction [64,65]. Initially characterized as chloroplastic proteins, some DUF538 proteins were shown to be in other cell compartments.…”

Maize glossy6 is involved in cuticular wax deposition and drought tolerance

“…However, plant DUF538 proteins are predicted to be the potential homolog of mammalian BPI (bactericidal/permeability increasing) proteins (Gholizadeh and Kohnehrouz, 2013), which have been suggested to be important for the defense system against various pathogens (Srivastava et al , 2007). Furthermore, BPI proteins are predicted to be structurally similar to esterase-type hydrolases, which implies DUF538 might have a lipid-associated enzymatic activity (Gholizadeh, 2014, 2016). The potential role of the gl6 gene in wax transportation may result from the interaction of the GL6 protein with other transporters, as has been shown in other systems (Park et al , 2013).…”