8.B.46. The Antimicrobial Snakin (ASN) Family
Snakin-1 (SN1) from potato is a cysteine-rich antimicrobial peptide with high evolutionary conservation. It has 63 amino acid residues after processing of the 88 aa precursor, 12 of which are cysteines capable of forming six disulfide bonds. SN1 localizes in the plasma membrane, and it is present mainly in tissues associated with active growth and cell division. SN1 is active in vitro against bacteria, fungus, yeasts, and even animal/human pathogens. It was shown that it also confers in vivo protection against commercially relevant pathogens in overexpressing potato, wheat, and lettuce plants. Although researchers have demonstrated SN1 can disrupt the membranes of E. coli, its integral antimicrobial mechanism remains unknown. It is likely that broad-spectrum antimicrobial activity is a combined outcome of membrane disruption and inhibition of intracellular functions. Besides, in potato, partial SN1 silencing affects cell division, leaf metabolism, and cell wall composition, thus revealing additional roles in growth and development. Its silencing also affects reactive oxygen species (ROS) and ROS scavenger levels. This finding indicates its participation in redox balance. Moreover, SN1 alters hormone levels, suggesting its involvement in the complex hormonal crosstalk. Altogether, SN1 has the potential to integrate development and defense signals directly and/or indirectly by modulating protein activity, modifying hormone balance and/or participating in redox regulation. Evidence supports a paramount role to SN1 in the mechanism underlying growth and immunity balance. Furthermore, SN1 may be a promising candidate in preservation, and pharmaceutical or agricultural biotechnology applications.
References:
Snakin-1 of 88 aas which may be processed by proteolisis. See family description for details (Almasia et al. 2020).
Snakin-1 (SN1) of Solanum tuberosum (potatoe)
Snakin-2 (SN2) of the potato and of 104 aas with 1 N-terminal TMS.
SN2 of Solanum tuberosum (potatoe)
Snakin-3 of Mentha longifolia (horsemint) of 114 aas and 1 N-terminal TMS. The defensive role of Snakin-3, a member of the subfamily III of Snakin/GASA peptides in potatoes has been illucidated (Nahirñak et al. 2024). Potato Snakin-3 functions as one of the defense Snakin/GASA proteins which share 12 cysteines in conserved positions in the C-terminal region. Most of them were involved in different aspects of plant growth and development, while a small number of these peptides were reported to have antimicrobial activity or participate in abiotic stress tolerance. In potato, 18 Snakin/GASA genes were identified and classified into three groups based on phylogenetic analysis (Nahirñak et al. 2024).
Snakin-3 of Mentha longifolia (horsemint)
Peamaclein-like protein of the Musa acuminata AAA Group of 91 aas with 1 N-terminal TMS.
Peamaclein-like protein of Musa acuminata
Uncharacterized protein of 94 aas with 1 N-terminal TMS.
UP of Rehmannia glutinosa
GAST1 protein of 88 aas and 2 TMSs, N-terminal and centrally located.
GAST1 of Ricinus communis (Castor bean)
GAST1 (GIBBERELLIN STIMULATED TRANSCRIPT RELATED PROTEIN) protein of 88 aas and 1 N-terminal TMS.
GAST1 protein of Cephalotus follicularis (Albany pitcher plant)