Phototropin localization and interactions regulate photophysiological processes in Chlamydomonas reinhardtii

Area of Science:

• * Molecular and Cellular Biology
• * Plant and Algal Physiology

Background:

• * Phototropin (CrPhot) is a blue-light sensing kinase crucial for photophysiological processes in algae, including phototaxis and photosynthesis.
• * CrPhot localizes to the eyespot and flagella in Chlamydomonas reinhardtii, but its full interaction network and regulatory roles are not well understood.

Purpose of the Study:

• * To identify novel protein partners of phototropin in C. reinhardtii.
• * To elucidate the mechanisms underlying phototropin's localization and regulatory functions.

Main Methods:

• * Utilized intraflagellar transport (IFT) mutants to study phototropin localization.
• * Employed CRISPR-Cas9 gene editing to generate phototropin knockouts.
• * Analyzed protein-protein interactions and gene expression levels.

Main Results:

• * Phototropin localization to flagella and eyespot is dependent on IFT.
• * Identified novel interactions between phototropin and photoreceptors (ChR1, ChR2, chlamyopsin 6), LOV-histidine kinases (LOV-HK1, LOV-HK2), and 14-3-3 protein.
• * Phototropin knockout mutants showed reduced ChR1 and 14-3-3 expression, impaired photomotility, and altered LOV-HK gene expression.

Conclusions:

• * This study reveals new insights into the phototropin interactome and its localization mechanisms in C. reinhardtii.
• * Findings advance the understanding of phototropin-mediated signal transduction and its role in cellular responses.