In Arabidopsis, 16 genes code for DEG proteases, which have different subcellular localizations and play an important role in protein quality control. DEG10 is a protease localized to mitochondria, of which the physiological function has been unclear so far. Analyses of plants expressing a GUS reporter gene under transcriptional control of the endogenous DEG10 promoter provided first information about the organ and tissue specificity of DEG10 expression. DEG10 is predominantly expressed in trichomes, but also in the vascular tissue of leaves, flowers and siliques. Beyond that, DEG10 is also expressed in roots. By phenotypic analyses of ∆deg10 mutants, we demonstrated that DEG10 critically contributes to primary root elongation. The defect in root growth in ∆deg10 mutants was even more pronounced at elevated temperatures, but it could be partially compensated by the supply with sucrose as external carbon source. It is conceivably that DEG10 might be important for protein quality control in mitochondria of roots. Additionally, we figured out that ∆deg10 mutants are characterized by reduced seed yield indicating a reduced evolutionary fitness. Moreover, respiration measurements revealed that ∆deg10 mutants by tendency show a decreased respiratory activity suggesting that ∆deg10 mutants are characterized by energy deprivation probably due to the impaired functionality of mitochondria. In the future, potential molecular targets of DEG10 shall be identified by quantitative LC-MS/MS analyses. By linking the molecular data with the phenotypic alterations of ∆deg10 mutants we hope to gain further insights into the physiological function of DEG10.

___

Barbara Jakobs conducted this work at the Chair of Biochemistry and Physiology at Konstanz University in the working group of Dr. Dietmar Funck.