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Article|01 Apr 2021|OPEN
Differential regulation of triterpene biosynthesis induced by an early failure in cuticle formation in apple
Luigi Falginella1,2, Christelle M. Andre3,4, Sylvain Legay4, Kui Lin-Wang3, Andrew P. Dare3, Cecilia Deng3, Ria Rebstock3, Blue J. Plunkett3, Lindy Guo3, Guido Cipriani1 & Richard V. Espley3,
1Dipartimento di Scienze Agroalimentari, Ambientali e Animali, University of Udine, Udine, Italy
2Research Center, Vivai Cooperativi Rauscedo, Rauscedo, Italy
3The New Zealand Institute for Plant and Food Research, Auckland, New Zealand
4The Luxembourg Institute of Science and Technology, Esch-surAlzette, Luxembourg

Horticulture Research 8,
Article number: 75 (2021)
doi: 10.1038/hortres.2021.75
Views: 217

Received: 03 Nov 2020
Revised: 08 Feb 2021
Accepted: 24 Feb 2021
Published online: 01 Apr 2021

Abstract

Waxy apple cuticles predominantly accumulate ursane-type triterpenes, but the profile shifts with the induction of skin russeting towards lupane-type triterpenes. We previously characterised several key enzymes in the ursane-type and lupane-type triterpene pathways, but this switch in triterpene metabolism associated with loss of cuticle integrity is not fully understood. To analyse the relationship between triterpene biosynthesis and russeting, we used microscopy, RNA-sequencing and metabolite profiling during apple fruit development. We compared the skin of three genetically-close clones of ‘Golden Delicious’ (with waxy, partially russeted and fully russeted skin). We identified a unique molecular profile for the russet clone, including low transcript abundance of multiple cuticle-specific metabolic pathways in the early stages of fruit development. Using correlation analyses between gene transcription and metabolite concentration we found MYB transcription factors strongly associated with lupane-type triterpene biosynthesis. We showed how their transcription changed with the onset of cuticle cracking followed by russeting and that one factor, MYB66, was able to bind the promoter of the oxidosqualene cyclase OSC5, to drive the production of lupeol derivatives. These results provide insights into the breakdown of cuticle integrity leading to russet and how this drives MYB-regulated changes to triterpene biosynthesis.