Auxin conjugate hydrolases in fragaria vesca contribute to iaa homeostasis and seedling growth

Authors: TANG, QIAN - University Of Minnesota; YU, PENG - University Of Minnesota; TILLMAN, MOLLY - University Of Minnesota; COHEN, JERRY - University Of Minnesota; Slovin, Janet

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/1/2018
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Auxin homeostasis in plants involves complex pathways for biosynthesis, conjugation to small molecules such as amino acids and to macromolecules such as proteins and complex carbohydrates, hydrolysis of these conjugates to release free IAA (indole 3-acetic acid) for growth and development, as well as utilization of IAA as a hormone and degradation pathways. Recently, using stable isotope labeling and high resolution LC-MS, we showed that unlike Arabidopsis, the diploid strawberry F. vesca hydrolyzes IAA-aspartate (IAasp) and IAA-glutamate (IAglu), the two IAA-amino acid conjugates found in the achenes, to release IAA for growth of the seedling. We also provided evidence that suggests that the hydrolysis reactions occur in different cellular compartments. The edible part of the strawberry, the receptacle, has long been known to enlarge in response to auxin produced by the developing achenes, the botanical true fruit. The classical literature describes a pattern of free auxin (indole-3-acetic acid; IAA) accumulation in the developing berry suggestive of active metabolic and/or transport activity that sustains the enlargement of the receptacle after embryo development is complete. If conjugated IAA moves from the developing achene for receptacle enlargement, as suggested by Kang et al (2013), IAA conjugate hydrolysis would play an important role in strawberry production. By homology to hydrolases from Arabidopsis, we have identified 6 IAA-amino acid hydrolase genes in the F. vesca genome. In silico analysis predicts that three of the encoded enzymes are localized to the chloroplast and three are most probably localized to the endoplasmic reticulum. Five of the six genes are expressed in growing seedlings, and three are expressed in early developing achenes (Hollender et al 2014). We have focused first on gene expression and cellular localization of FveILL3, an IAA-amino acid hydrolase related to Medicago truncatula IAR33, which has been shown to hydrolyze IAasp. FveILL3, like Arabidopsis ILL3, is predicted to localize to the chloroplast and does not have a KDEL type endoplasmic reticulum retention sequence.