Spatial Distribution of Astins in Aster tataricus and Their Production by Cyanodermella asteris

TL;DR

A study reveals that certain anticancer peptides called astins in the plant Aster tataricus are produced by an endophytic fungus, not the plant itself.

Contribution

The study shows that the fungus Cyanodermella asteris can produce a wider variety of astins than previously known, including new ones.

Findings

Astins C, F, and G are produced by the fungus Cyanodermella asteris, not the plant Aster tataricus.

The fungus produces more astin diversity, including new astins, under high salinity conditions.

Astins are nonhomogeneously distributed in the plant and likely colocalize with fungal cells.

Abstract

Aster tataricus is a plant
used
in Traditional Chinese Medicine for the treatment of cough, phlegm,
and asthma. Phytochemical studies of A. tataricus have resulted in the isolation of 23 peptides, among which the astins
are recognized for their potential application as anticancer drugs.
However, it was found that some of the astins, namely, astins C, F
and G, are in fact produced by an endophytic fungus, Cyanodermella asteris, isolated from the inflorescences
of the plant, while the remainder were suggested to be transformation
products of these astins by A. tataricus. Using mass spectrometry imaging and microscopy, we demonstrate
that astins exhibit a nonhomogeneous distribution, vary in relative
abundance in different plant tissue sections, and are likely colocalized
with fungal cells. To gain further insights into the diversity and
composition of astins produced by C. asteris, we applied HPLC–MS/MS and mass spectrometry-based molecular
networking after in vitro cultivation of the fungus
in media with increased salinity. We found that the fungus produced
a higher variety of astins than previously known, including several
yet undescribed astins, suggesting that the fungus alone is indeed
able to produce the complete astin diversity and that cross-species
biosynthesis is unlikely.

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