Phytohormone profiling in an evolutionary framework

Abstract

The genomes of charophyte green algae, close relatives of land plants, typically do not show signs of developmental regulation by phytohormones. However, scattered reports of endogenous phytohormone production in these organisms exist. We performed a comprehensive analysis of multiple phytohormones in Viridiplantae, focusing mainly on charophytes. We show that auxin, salicylic acid, ethylene and tRNA-derived cytokinins including cis-zeatin are found ubiquitously in Viridiplantae. By contrast, land plants but not green algae contain the trans-zeatin type cytokinins as well as auxin and cytokinin conjugates. Charophytes occasionally produce jasmonates and abscisic acid, whereas the latter is detected consistently in land plants. Several phytohormones are excreted into the culture medium, including auxin by charophytes and cytokinins and salicylic acid by Viridiplantae in general. We note that the conservation of phytohormone biosynthesis and signaling pathways known from angiosperms does not match the capacity for phytohormone biosynthesis in Viridiplantae. Our phylogenetically guided analysis of established algal cultures provides an important insight into phytohormone biosynthesis and metabolism across Streptophyta.

Origin and evolution of Auxin Efflux Carrier family: PIN, PILS, GPR155 and the others

“…If we look outside the terrestrial plant, we do not find homologs of the canonical auxin F-box protein family receptor-based signalling pathway, nor do we even find homologs of key genes for auxin synthesis. However, we do find the IAA and its metabolites across the whole green lineage (Schmidt et al, 2024) and an apparent conservation of auxin carrier genes ensuring auxin export from the cytoplasm, namely, proteins from the PIN-FORMED (PIN) and PIN-LIKES (PILS) families (Carrillo‐Carrasco et al, 2023; Vosolsobě et al, 2020). While the former family has been intensively studied for several decades, as its members are among the most important morphogenetic regulators in plants, PILS were discovered only a decade ago (Barbez et al, 2012; Feraru, 2012) and, in contrast to PINs, only provide homeostatic regulation of auxin levels in the cell, not its export from the cell to the environment.…”