Poster: Integrative plant physiology

Abs # 33: Autophagy in plants: Identification of putative homologs in Arabidopsis, expression of autophagy genes in response to nutrient stress, and molecular characterization of AtATG6.

Presenter:	Harrison-Lowe, Nicola , nhlowe@umich.edu
Authors	Harrison-Lowe, Nicola  (A)   Yerram, Mamatha  (B)   Laporte, Marianne  (B)   Olsen, Laura J. (A)
Affiliations:	(A): University of Michigan (B): Eastern Michigan University

Autophagy is a regulated recycling process that enables organisms to survive during various stress conditions through the breakdown of cellular constituents. While extensively studied in yeast and mammalian systems, this process has not been well characterized in plants. We have begun a multi-faceted investigation to understand plant autophagy. First, standard bioinformatics techniques were used to identify putative autophagy genes in both Arabidopsis and rice genomes. Although at least 27 genes are directly involved in autophagy in yeast, homologs of only 16 are easily identified in Arabidopsis. Second, an Arabidopsis cell-culture system was developed to determine the environmental conditions that will induce autophagy. We have used this system to identify potential molecular markers for autophagy using RT-PCR. Expression of the Arabidopsis homologs to the yeast genes ATG3, ATG6, and ATG9 increased over time in response to nitrogen deficiency. Third, we have identified a series of TDNA-insertion mutants with putative defects in predicted autophagy genes in Arabidopsis. The analysis of these lines includes biochemical, molecular, and ultrastructural characterization. Finally, we have focused on the role of AtATG6 in plant autophagy. Mutants homozygous for a TDNA insert in AtATG6 are not viable, but the lines can be maintained as heterozygotes. The proteins that interact with ATG6 in plants are completely unknown; the homologs to the yeast genes have not been found in the Arabidopsis genome. Identification of the proteins that interact with AtATG6 may provide new insights into the role of this protein in autophagy and the process of plant autophagy in general.