TITLE:
Chroococcidiorella tianjinensis gen. et sp. nov. (Trebouxiophyceae, Chlorophyta), a Green Alga Arises from the Cyanobacterium TDX16
AUTHORS:
Qinglin Dong, Xiangying Xing
KEYWORDS:
Green Algae, Cyanobacterial Origin, Chroococcidiorella tianjinensis, 18S rRNA Gene Sequence, Ultrastructure
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.11 No.11,
November
30,
2020
ABSTRACT: All algae documented so far
are of unknown origin. Here, we provide a taxonomic description of the first
origin-known alga TDX16-DE that arises from the Chroococcidiopsis-like endosymbiotic cyanobacterium
TDX16 by de novo organelle biogenesis after acquiring its green algal host Haematococcus pluvialis’s DNA. TDX16-DE
is spherical or oval, with a diameter of 2.0-3.6 μm, containing typical
chlorophyte pigments of chlorophyll a, chlorophyll b and lutein and reproducing
by autosporulation, whose 18S rRNA gene sequence shows the highest similarity
of 99.7% to that of Chlorella vulgaris.
However, TDX16-DE is only about half the size of C. vulgaris and structurally similar to C. vulgaris only in having a chloroplast-localized pyrenoid, but
differs from C. vulgaris in that 1)
it possesses a double-membraned cytoplasmic envelope but lacks endoplasmic
reticulum and Golgi apparatus; and 2) its nucleus
is enclosed by two sets of envelopes (four unit membranes). Therefore, based on these characters and the cyanobacterial
origin, we describe TDX16-DE as a new genus and species, Chroococcidiorella tianjinensis gen. et sp. nov., which sets the
basis for multidisciplinary research.