Characterization of ATPase Assembly Proteins Expressed under Mitochondrial Retrograde Regulation in Arabidopsis thaliana

When under environmental stresses, plant mitochondria initiate a signaling pathway, called mitochondrial retrograde regulation (MRR), to alter nuclear gene expression and help plants survive.  Previous research indicates that small heat shock proteins (sHSPs) are increased in expression due to MRR in plants.  Under heat stress, sHSPs act as chaperones to protect proteins involved in important cellular functions.  Like sHSPs, ATPase Assembly Proteins (AAPs) are increased in expression during several biotic and abiotic stresses and in response to MRR.  Although AAP expression and function are not well characterized, these proteins are thought to be important for normal functioning mitochondria and general stress responses of plants.  Practical applications of this research include the potential production of crops that are less susceptible to environmental stresses.

We identified Arabidopsis genes encoding proteins similar to yeast AAPs, which are strongly increased in expression by MRR and during stresses such as pathogen attack.  If these genes encode AAPs, then these will be the first AAP genes in plants to be extensively studied in relation to MRR and stress responses, will provide a better understanding of MRR and define a new category of proteins involved with stress.  Using classical molecular biology and microbial genetics techniques, we determined the expression patterns of putative AAP genes: At2g41730, At5g24640 and At5g40690 under normal and stress conditions, and tested knock out lines and AAP gene over-expresser lines in order to determine whether or not this new family of putative AAPs has a role in stress responses in plants.