What is it about?

A metabolic pathway is described that impacts the aroma of apple fruit. It uses two simple products of primary metabolism and shunts them into a pathway, previously only found in bacteria, that leads to the formation of numerous aroma-active esters

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Why is it important?

Scent is one of the primary means for organisms, including humans, to locate food and evaluate its edibility. In fruits, esters are often the predominant class of odor-active compounds. However, our understanding as to how plants make esters is rudimentary. In ripening apple, the supposition has been that the precursors to esters come from degradative reactions. This work demonstrates quite the opposite. A pathway is turned on during apple ripening that takes two of the most fundamental metabolites in plants, pyruvate and acetyl-CoA, and generates esters that impact aroma. Interestingly, the pathway has no feedback regulation, leading to aroma production that persists even as fruits ripen and senesce.


This work is from a rather practical laboratory where aroma biosynthesis is not the main focus. As a result, the work was aggregated over time, spanning 15 years. It builds on opportunity, interest and talent of individuals who have been able to contribute over the years. It is a testament to an original 'good idea' with which the collaborators persisted to shine a light on a rather under appreciated area of biological science - the generation of scent.

Randolph Beaudry
Michigan State University

Read the Original

This page is a summary of: Citramalate synthase yields a biosynthetic pathway for isoleucine and straight- and branched-chain ester formation in ripening apple fruit, Proceedings of the National Academy of Sciences, January 2021, Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2009988118.
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