The closest relative of Archaeplastida is revealed by phylogenomic analyses that include Microheliella maris

By clarifying the phylogenetic positions of “orphan” protists (unicellular
micro-eukaryotes with no affinity to extant species/lineages), we may
uncover the novel affiliation between two (or more) major lineages in
eukaryotes. Microheliella maris was an orphan protist, which failed to be
placed within the previously described species/lineages by pioneering
phylogenetic analyses. In this study, we analyzed a 319-gene alignment and
demonstrated that M. maris represents a basal lineage of one of the major
eukaryotic lineages, Cryptista. We here propose a new clade name
“Pancryptista” for Cryptista plus M. maris. The 319-gene analyses also
indicated that M. maris is a key taxon to recover the monophyly of
Archaeplastida and the sister relationship between Archaeplastida and
Pancryptista, which is collectively called as “CAM clade” here.
Significantly, Cryptophyceae tend to be attracted to Rhodophyta depending
on the taxon sampling (ex., in the absence of M. maris and Rhodelphidia)
and the particular phylogenetic ‘signal’ most likely hindered the stable
recovery of the monophyly of Archaeplastida in previous studies.