Identification and Characterization of ATP-Binding Cassette Transporters in Chlamydomonas reinhardtii

Abstract

Microalgae are promising microorganisms used to produce value-added products or to develop sustainable approaches for environmental remediation. The ATP-binding cassette proteins (ABCs) of Chlamydomonas reinhardtii have been characterized as indispensable transporters for CO2 concentrating mechanism, lipid biosynthesis, and heavy metal sequestration. However, few microalgal ABC proteins have been studied compared with higher plants or non-photosynthetic microorganisms. This study performed a genome-wide, evolutionary, and transcriptomic survey of C. reinhardtii ABC proteins (CrABCs). A total of 75 CrABCs were identified and classed into eight ABC subfamilies, from ABCA to ABCI. We found that no whole or partial genome duplication events occurred in C. reinhardtii after the ancient endosymbiosis events, but gene duplications occurred in a small range of chromosomal regions, which forced ABC family expansion. Abundant light, abscisic acid, and jasmonic acid response cis-elements were mapped in the CrABC promoters, coinciding with the evolutionary history of hormone signaling in Chlorophyta. The expression survey under light/dark rhythms revealed a close bond of CrABCs with cell division and development. A broad study of CrABCs supported their expected roles in heavy metal detoxification, lipid metabolism, and environmental adaptation. Moreover, the evolutionary and expression survey predicted the functions of unknown CrABCs, which are elaborated in the text. Two half-size CrABCGs—CrABCG3 and CrABCG26—were described as plasma-membrane transporters that might participate in lipidic compound secretion. This study provides fundamental and exhaustive information about CrABCs, which are indispensable for the functional elucidation of ABC proteins in microalgae.

TurboID reveals the proxiomes of Chlamydomonas proteins involved in thylakoid biogenesis and stress response

“…Among these, VPL4, 5, 8, and 10 were enriched only under H 2 O 2 stress. According to InterPro ( Blum et al 2021 ), VPL5, 6, 8, and 10 have no functional domains, VPL4 and VPL7 are kinases, VPL9 is a chlorophyllase, cleaving off the phytol tail from chlorophyll, and VPL11 is a half-size ABC transporter recently named ABCB4 ( Li et al 2022 ). Predalgo predicts VPL11/ABCB4 to localize to mitochondria, while VPL1-10 are all predicted to localize to the chloroplast.…”

Phylogenetic analysis ofABCEgenes across the plant kingdom

“…Based on the data from the public databases and our analysis we were able to reconfirm the same number of ABCE genes for a selection of plant species. For example there is a single gene in C. hirsuta (Kougioumoutzi et al 2013), in C. reinhardtii (Li et al 2022), in Citrus sinesis and in Theobroma cacao (Navarro-Quiles et al 2022). Similarly to previous studies, we reverified two genes in Zea mays (Pang et al 2013), in tomato (Ofori et al 2018), in rice, and in Populus trichocarpa (Navarro-Quiles et al 2022).…”