A Novel Multivariate Analysis: Overturning Long-Held Beliefs About Non-Photochemical Quenching.

Abstract

When light absorption exceeds photochemical quenching, plants activate non-photochemical quenching (NPQ) to dissipate excess energy as heat. Recently, we have developed a novel multivariate pipeline for NPQ induction analysis. Applying this pipeline to NPQ induction curves of several Arabidopsis thaliana NPQ genotypes, overturns the long-held belief that zeaxanthin (Zx) accelerates NPQ induction upon light-adaptation. We demonstrate that the observed acceleration is solely due to the action of PsbS. Our approach allows the synergistic inter-relationships between PsbS and Zx to be unambiguously explored. Specifically, we applied our analysis to dark- and light-adapted wild-type (wt), Zx-lacking (npq1), Zx-rich (npq2) and PsbS-lacking (npq4) A. thaliana. Only the PsbS-dependent quenching in npq2, wt and npq1 plants exhibited faster induction kinetics following light adaptation. Changes in the Zx-levels (npq1 → wt → npq2) lead to changes in the overall amplitudes of the PsbS-components, revealing a Zx-driven amplification of PsbS-dependent quenching. In the presence of PsbS (npq2/wt), Zx also provides its own distinct contribution to NPQ. Together, this reveals the distinct roles of Zx in NPQ and the multilayered synergistic relationship between PsbS and Zx. Combined with mutant genotypes, our unique analysis is an invaluable toolkit to answer mechanistic questions and will allow different NPQ models to be experimentally explored.