Neofunctionalised plastid translocon regulates chloroplast ageing in Arabidopsis
- 1University of Oxford
Abstract
Protein import across the chloroplast outer membrane is mediated by the TOC complex and regulated by GTP hydrolysis at two receptor GTPases, large and small. The former are the {beta}-barrel-containing Toc159 family of proteins (Sun and Jarvis 2023; H. Li and Chiu 2010; Shi and Theg 2013a; Kessler and Schnell 2009). The smallest member of this family in higher plants is Toc90, which has long been regarded as functionally unimportant due to the absence of obvious phenotypes in early mutant studies (Kubis et al. 2004; Infanger et al. 2011a). It was hypothesised that Toc90 is a relic of an ancestral Toc159 protein from early green lineage organisms (Hofmann and Theg 2003; Reumann et al. 2005). Here, we challenge this view by combining genetic, biochemical, phylogenetic, and in silico structural analyses to show that Toc90 is not an ancient remnant, but rather a neofunctionalised derivative of Toc159, and likely the most recently evolved member of the family. We show that Toc90 physically associates with Toc33 as a part of a photosynthetic TOC complex. Furthermore, we identify Toc90 as a regulator of chloroplast ageing. Our findings redefine Toc90 as an active and specialised component of the chloroplast protein import machinery, playing a pivotal role in senescence, especially in reducing photosynthetic protein abundance. Together, these results highlight Toc90 as a promising target for manipulating chloroplast longevity and plant senescence, with potential to improve crop productivity and yield.
Related
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BibTeX
@misc{bag2026neofunctionalised,
title = {{Neofunctionalised plastid translocon regulates chloroplast ageing in Arabidopsis}},
author = {P. Bag and P. Lymperopoulos and A. Lau and B. Peixoto and C. Grundy and S. Kubis-Waller and R. Patel and R. P. Jarvis},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.29.755046},
url = {https://www.biorxiv.org/content/10.64898/2026.09.29.755046v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Neofunctionalised plastid translocon regulates chloroplast ageing in Arabidopsis
AU - P. Bag
AU - P. Lymperopoulos
AU - A. Lau
AU - B. Peixoto
AU - C. Grundy
AU - S. Kubis-Waller
AU - R. Patel
AU - R. P. Jarvis
PY - 2026
DA - 2026/09/29
PB - bioRxiv
DO - 10.64898/2026.09.29.755046
UR - https://www.biorxiv.org/content/10.64898/2026.09.29.755046v1
AB - Protein import across the chloroplast outer membrane is mediated by the TOC complex and regulated by GTP hydrolysis at two receptor GTPases, large and small. The former are the {beta}-barrel-containing Toc159 family of proteins (Sun and Jarvis 2023; H. Li and Chiu 2010; Shi and Theg 2013a; Kessler and Schnell 2009). The smallest member of this family in higher plants is Toc90, which has long been regarded as functionally unimportant due to the absence of obvious phenotypes in early mutant studies (Kubis et al. 2004; Infanger et al. 2011a). It was hypothesised that Toc90 is a relic of an ancestral Toc159 protein from early green lineage organisms (Hofmann and Theg 2003; Reumann et al. 2005). Here, we challenge this view by combining genetic, biochemical, phylogenetic, and in silico structural analyses to show that Toc90 is not an ancient remnant, but rather a neofunctionalised derivative of Toc159, and likely the most recently evolved member of the family. We show that Toc90 physically associates with Toc33 as a part of a photosynthetic TOC complex. Furthermore, we identify Toc90 as a regulator of chloroplast ageing. Our findings redefine Toc90 as an active and specialised component of the chloroplast protein import machinery, playing a pivotal role in senescence, especially in reducing photosynthetic protein abundance. Together, these results highlight Toc90 as a promising target for manipulating chloroplast longevity and plant senescence, with potential to improve crop productivity and yield.
ER -