# Nitric oxide delays yellowing by regulating chloroplast membrane lipid metabolism and the ascorbate–glutathione cycle in postharvest broccolini

## TL;DR

Nitric oxide (NO) delays yellowing in postharvest broccolini by protecting chloroplast membranes and enhancing antioxidant systems.

## Contribution

This study reveals a novel mechanism by which NO delays yellowing through lipid metabolism and the ascorbate-glutathione cycle in broccolini.

## Key findings

- GSNO treatment delayed yellowing by 4 days and preserved chloroplast membrane structure.
- NO enhanced chloroplast membrane lipids and ascorbate-glutathione cycling, reducing oxidative damage.
- GSNO upregulated BoPPT1, a protein involved in chloroplast membrane regulation.

## Abstract

NO plays an important role in regulating fruit and vegetable postharvest quality. However, its mechanisms of action in delaying postharvest yellowing of vegetables remains poorly understood.

To elucidate this, we examined the effects of an NO scavenger (cPTIO), and an exogenous NO donor (GSNO), on broccolini postharvest yellowing. Furthermore, the mechanism by which NO delays the postharvest chlorosis process of broccolini was revealed through the membrane lipid metabolism and ascorbate-glutathione cycle pathways.

Evaluation of color and chlorophyll content revealed that GSNO treatment delayed yellowing by 4 days relative to the control. The chloroplast membrane remained well developed during the entire storage process following GSNO treatment, whereas it began to collapse 4 days after cPTIO treatment. GSNO maintained cell-membrane permeability, increased levels of chloroplast membrane lipids (monoglycosyldiacylglycerol, phosphatidylglycerol, and digalactosyldiacylglycerol), improved ω-3 FAD enzyme activity, enhanced ascorbate–glutathione cycling, and promoted BoFAD8 transcription, thus promoting 18/16:3-triene fatty acid accumulation. GSNO upregulated BoPPT1, which was identified as a chloroplast membrane-spanning protein that participates in regulating chloroplast morphology.

NO alleviated oxidative damage to the chloroplast membrane lipid system, thereby delaying broccolini yellowing. The results of this study may provide novel insights for developing postharvest quality control technologies for broccolini and the genetic improvement of broccolini varieties.