Evidence for Exaptation of the Marchantia polymorpha M20D Peptidase MpILR1 into the Tracheophyte Auxin Regulatory Pathway

Physcomitrium patens Mutants in Auxin Conjugating GH3 Proteins Show Salt Stress Tolerance but Auxin Homeostasis Is Not Involved in Regulation of Oxidative Stress Factors

“…While the GH3 proteins of P. patens are similar in sequence and function to the higher plant enzymes [ 15 ], the hydrolysis pathway was thought not to take place at all, since the typical plant sequences for conjugate hydrolases were missing [ 75 ]. However, recent work provided experimental evidence for the possible hydrolysis of IAA amino acid conjugates in P. patens as well, since it was found that the moss contained sequences similar to bacterial auxin amidohydrolases [ 24 , 76 ] and its capacity to cleave some conjugates in vivo and in vitro [ 24 ]. These sequences were possibly acquired by horizontal gene transfer [ 76 ].…”

“…However, several lines of evidence presented point to a horizontal gene transfer from bacteria for the genes identified so far [ 23 ]. In liverworts, conjugation and hydrolysis is most likely taking place already via conjugation and hydrolysis, according to the genes annotated in the respective genomes [ 24 , 25 ]. In contrast to the hydrolase present in P. patens , in Marchantia polymorpha a precursor enzyme of the vascular plant type has been identified [ 25 ].…”

Amino acid conjugation of oxIAA is a secondary metabolic regulation involved in auxin homeostasis

“…Nonetheless, the GH3-ILR1-DAO pathway can unlikely regulate IAA metabolism in lower-land plants. DAO-like enzymes evolved specifically with angiosperms, ILL enzymes were not found in the moss P. patens, and the Marchantia polymorpha ILR1 is not employed in auxin conjugate hydrolysis in this liverwort (Campanella et al, 2018(Campanella et al, , 2019Brunoni et al, 2020;Takehara et al, 2020), suggesting that yet-to-be-discovered enzymes could be responsible for oxidation and hydrolysis reactions in lower vascular plants. Altogether, the GH3-mediated oxIAA conjugation is a metabolic pathway that occurred early during plant evolution, and its contribution to IAA homeostasis is species-dependent.…”

On the Evolutionary Origins of Land Plant Auxin Biology

“…ILR1 homologs are found broadly (Fig. 1), but not ubiquitously, throughout Streptophytes and even cyanobacteria (Campanella et al 2014(Campanella et al , 2018(Campanella et al , 2019. Three P. patens genes have activity against a variety of auxin-aa conjugates (Campanella et al 2019), but their higher sequence similarity and codon usage to bacterial (B) Phylogenetic reconstruction of the GH3 protein family.…”