Examination of the M20D Auxin Conjugate Peptidase Family from Hornwort and Implications on the Evolution of the Tracheophytes

• Published in: Journal of plant growth regulation 2022-10, Vol.41 (7), p.2695-2706
• Main Authors: Medina, Edgar A., Desind, Samuel, Hallak, Abdulkader, Alhaddad, Abdullah, Smalley, John V., Campanella, James J.
• Format: Article
• Language: English
• Subjects: Activity recognition; Agriculture; Aquatic plants; Auxins; Biomedical and Life Sciences; Conjugates; Enzymes; Homology; Hydrolase; Life Sciences; Megaceros; Paraphymatoceros hallii; Peptidase; Peptidases; Phaeoceros carolinianus; Phylogeny; Plant Anatomy/Development; Plant Physiology; Plant Sciences; Sequence analysis; Substrates; Three dimensional analysis
• ISSN: 0721-7595; 1435-8107
• DOI: 10.1007/s00344-021-10467-3

We have identified and cloned five auxin conjugate amidohydrolases (M20D peptidases) in four different hornwort species ( Phaeoceros carolinianus , Megaceros tosanus , Megaceros vincentianus , and Paraphymatoceros hallii ). Sequence analysis suggests that all five enzymes have greater than 60% overall similarity to tracheophyte amidohydrolases. Phylogenetic analysis supports the hypothesis that the bryophyte and tracheophyte hydrolases are derived from a common ancestor. Enzyme studies of hornwort auxin amidohydrolases all demonstrate greater activity and substrate recognition than the more ancient liverwort hydrolase (MpILR1). The mean wild-type hornwort hydrolytic activity (23.2 ± 6.8 pmol auxin released/min/ml), although higher than the liverwort activity (1.3 ± 1.1 pmol auxin released/min/ml), was almost a magnitude lower than the average activity in tracheophyte hydrolases (186.2 ± 52.1 pmol auxin released/min/ml). Two hornwort orthologues from M. vincentianus and M. tosanus possess a Glycine238/240 replacing the tracheophytically conserved Serine209, while two from P. hallii and P. carolinianus have an Alanine238 at that homologous residue location. Further enzymatic studies and three-dimensional structural analyses of the hornwort enzymes present supporting evidence that the Ala238-line of hornworts is the likely clade from which tracheophytes arose.