Comparing Four Red/Green-Leafed Vegetables Reveals the Complementary Photoprotective Roles of Anthocyanin Accumulation and Chlorophyllase

TL;DR

This study compares red and green leafy vegetables to understand how anthocyanins and chlorophyllase protect plants from high light.

Contribution

The study reveals that chlorophyllase activity compensates for the lack of anthocyanin photoprotection in green leaves.

Findings

Green-leafed varieties showed higher chlorophyllase activity than red ones under normal and high-light conditions.

Red Ramosa and Asparagus lettuce had worse high-light tolerance than their green counterparts.

In Arabidopsis, anthocyanin-deficient mutants induced higher chlorophyllase expression.

Abstract

The photoprotective role of anthocyanins in leaves is debated, as some anthocyanin-rich red leaves do not exhibit greater tolerance to high-light conditions than their anthocyanin-deficient green counterparts. In this study, we studied four leafy vegetables with both red- and green-leafed varieties: Bok Choy and Choy Sum from Brassica rapa, and Ramosa and Asparagus lettuce from Lactuca sativa. Under normal-light conditions, the red cultivars accumulated anthocyanins, the green ones did not, and all presented no photoinhibition. However, the green-leafed varieties exhibited 3–5-fold higher chlorophyllase (CLH) activity than their red counterparts. Under high-light conditions, more anthocyanins were accumulated in the red cultivars, but again, none accumulated in the green cultivars; the green cultivars showed greater CLH activity than their red counterparts. Bok Choy and Choy Sum demonstrated comparable photoinhibition between their red and green counterparts, with a similar reduction in photosynthetic activity, Fv/Fm, ETR, and NPQ; red Ramosa and Asparagus lettuce exhibited worse high-light tolerance than their green counterparts, with greater reductions in Fv/Fm and ETR. In Arabidopsis, the anthocyanin-deficient mutant tt3tt4 (green) also induced higher AtCLH1/2 expression than the wild-type and constitutive anthocyanin accumulation line PAP1-D (red); the AtCLH1 overexpressor and the clh1-1/2-2 mutant accumulated less and more anthocyanin than the wild-type, respectively. The findings suggest that CLH induction may compensate for absent anthocyanin photoprotection in green cultivars and that the two strategies may play complementary roles in photoprotection.

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