Biology subjects

Peixoto, B.

Publications and source records attributed to Peixoto, B..

3 recordsLinked to original sources

bioRxiv2026

Neofunctionalised plastid translocon regulates chloroplast ageing in Arabidopsis

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.

plant biology↗

bioRxiv2025

TPS Proteins coordinate plant growth with sugar availability via the SnRK1 Kinase

The ability to sense and respond to nutrients determines adaptation and survival in all organisms. In plants, sucrose stimulates growth and developmental progression via the signalling sugar trehalose 6-phosphate (T6P) which reflects sucrose availability. T6P acts, at least partly, by inhibiting the protein kinase SUCROSE NON-FERMENTING 1 (SNF1)-RELATED KINASE 1 (SnRK1) but the underlying mechanisms are poorly understood. Here, we identify a group of catalytically inactive T6P synthase (TPS) proteins, TPS5/6/7, as important factors for coupling the T6P signal to SnRK1 activity. In Arabidopsis thaliana, lack of TPS5/6/7 causes severe growth defects, particularly in roots. This is accompanied by a metabolic signature that is suggestive of T6P insensitivity and impaired sucrose utilization. Using a combination of genetics, SnRK1 activity assays, and imaging, we demonstrate that the growth defects of the tps5/6/7 mutant are due to SnRK1 misregulation and are reverted by knocking-down SnRK1 in this background. Co-immunoprecipitation assays further show that T6P promotes the interaction of TPS proteins with SnRK1 in a highly specific and dose-dependent manner. Our results support a model where TPS proteins act as T6P sensors, inhibiting non-nuclear SnRK1 activity when sucrose is abundant to promote biosynthetic processes and growth.

plant biology↗

bioRxiv2023

HOS1 promotes plant tolerance to low-energy stress via the SnRK1 protein kinase

Plants need to integrate internal and environmental signals to mount adequate stress responses. The NUCLEAR PORE COMPLEX (NPC) component HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES 1 (HOS1) is emerging as such an integrator, affecting responses to cold, heat, light and salinity. Stress conditions often converge in a low-energy signal that activates SUCROSE NON-FERMENTING 1-RELATED KINASE 1 (SnRK1) to promote stress tolerance and survival. Here, we explored the role of HOS1 in the SnRK1-dependent response to low-energy stress in Arabidopsis thaliana, using darkness as a treatment and a combination of genetic, biochemical and phenotypic assays. We show that the induction of starvation genes and plant tolerance to prolonged darkness are defective in the hos1 mutant. HOS1 interacts physically with the SnRK11 catalytic subunit in yeast-two-hybrid and in planta, and the nuclear accumulation of SnRK11 is reduced in the hos1 mutant. Likewise, another NPC mutant, nup160, exhibits lower activation of starvation genes and decreased tolerance to prolonged darkness. Importantly, defects in low-energy responses in the hos1 background are rescued by fusing SnRK11 to a potent nuclear localization signal, or by sugar supplementation during the dark treatment. Altogether, this work demonstrates the importance of HOS1 for the nuclear accumulation of SnRK11, which is key for plant tolerance to low-energy conditions.

plant biology↗