Gradients of adenylate nucleotides and energy charge within ‘Rocha’ pear fruit

Cellular energy status is central for metabolic regulation.
Pear fruit is stored for several months and its fruit anatomy, surface-to-volume ratio, and gas exchange properties may result in uncharacterized gradients in adenylate nucleotides.
The aim of this work was to characterize the axial and radial gradients of adenylate nucleotides and energy charge in pear fruit. ‘Rocha’ pear (Pyrus communis L.) fruits with 55-60 mm were sampled after 3 months under controlled atmosphere storage, in a mature but unripe stage.
Fruits were sectioned transversely in skin (1.5 mm thick), outer flesh (10 mm thick under skin), and inner flesh (10 mm thick under outer flesh) and longitudinally in three-thirds, proximal, medial, and distal.
The sections were freeze-dried and adenosine 5′-triphosphate (ATP), adenosine 5′-diphosphate (ADP) and adenosine 5′-monophosphate (AMP) measured by bioluminescence.
Adenylate energy charge (AEC) was calculated as: AEC = [[ATP] + 0.5[ADP]] / [[ATP] + [ADP] + [AMP]]. A radial AEC gradient was measured in the fruit but no significant gradient was observed from the proximal to the distal fruit sections.
Total pool of nucleotides, on a fresh mass basis, was 865.7 nmol g^-1 in the skin, 438.1 nmol g^-1 in the outer flesh, and 585.6 nmol g^-1 in the inner flesh.
AEC was 0.80, 0.72, and 0.69 in the skin, outer, and inner flesh, respectively.
AMP levels were less than 11% of the total nucleotide pool.
ATP accounted for 70, 53, and 46% of the total adenylate nucleotides, in the skin, outer, and inner flesh, respectively.
In conclusion, there was variation in energy charge in the radial direction, with lower values at the fruit center.
Whether this transversal gradient is related to susceptibility of internal browning disorders remains to be clarified.

VIII International Postharvest Symposium: Enhancing Supply Chain and Consumer Benefits – Ethical and Technological Issues

D.P.F. Almeida, A.A. Saquet

ATP, ADP, AMP, fruit quality, Pyrus communis

https://doi.org/10.17660/ActaHortic.2018.1194.172