Morphology, fine structure, life cycle and phylogenetic analysis ofPhyllosiphon arisari, a siphonous parasitic green alga

Abstract

Phyllosiphon arisari Ku¨hn (Phyllosiphonaceae, Chlorophyta) commonly occurs in Arisarum leaves in coastal Mediterranean areas of the Iberian Peninsula and Balearic islands. The genus Phyllosiphon was first considered to be a member of the Xanthophyceae but was later transferred to the chlorophytes. However, there are few data about its morphology, ultrastructure, ecology or phylogenetic affinities. In this paper we describe the morphology of Phyllosiphon, as studied in field material and in culture; the fine structure, analysed by transmission electron microscopy; and phylogenetic relationships, inferred from DNA sequences. The siphonous filaments were seen to divide and penetrate leaf tissues. The cytoplasm divided into spherical or subspherical sporocysts producing autospores inside. Cytoplasmic remains could be observed between autospores or on their cell walls. Phylogenetic analysis of 18S rDNA and 16S rDNA sequences showed that the closest relatives of Phyllosiphon are subaerial strains of Heterochlorella, Heveochlorella and Kalinella, demonstrating that Phyllosiphon should be transferred to Trebouxiophyceae. An evolution from unicells to a siphonous thallus, and from aerophytic to endophytic and parasitic habits, is proposed for Trebouxiophyceae.

Leptochlorella corticola gen. et sp. nov. and Kalinella apyrenoidosa sp. nov.: two novel Chlorella-like green microalgae (Trebouxiophyceae, Chlorophyta) from subaerial habitats

“…K. bambusicola was isolated from a tropical ecosystem and K. apyrenoidosa was found in a part of the Mediterranean with a humid subtropical climate, according to the Köppen-Geiger climate classification system (Peel et al, 2007). In addition, the phylogenetically closely related genera Heveochlorella and Phyllosiphon were also found in various subtropical or tropical subaerial localities (Zhang et al, 2008;Aboal & Werner, 2011). Therefore, we expect that additional taxa of the Heterochlorella lineage might be discovered in the little-known phototrophic microbial biofilms of these habitats.…”

Molecular diversity of green corticolous microalgae from two sub-Mediterranean European localities

“…Kalinella apyrenoidosa, one of the two species of the genus Kalinella, was recently described from a sub-Mediterranean corticolous sample (Neustupa et al, 2013a). The life cycle of a peculiar and little-known genus Phyllosiphon, another member of the Watanabea clade, probably includes chlorelloid subaerial individuals, as well as siphonaceous parasitic populations thriving in the leaves of the subtropical vascular plant genus Arisarum (Aboal & Werner, 2011;Hallmann et al, 2013).…”

Phyllosiphon ari sp. nov. (Watanabea clade, Trebouxiophyceae), a new parasitic species isolated from leaves of Arum italicum (Araceae)<br />

“…Our analyses, expanded by newly acquired 18S rDNA and rbcL gene sequences from parasitic populations of the Phyllosiphon from infected leaves of Arisarum vulgare in Sardinia and Croatia, show that these microalgae represent a single homogenous lineage that was previously identified as P. arisari (Aboal & Werner 2011, Procházková et al 2015a. However, phylogenetic investigation of parasitic specimens isolated from infected leaves of Arum italicum showed that these parasitic microalgae formed a lineage separated from P. arisari.…”

“…The only known DNA sequences of the parasitic members of the Phyllosiphon were acquired from infected leaves of subtropical Arisarum vulgare (Aboal & Werner 2011, Procházková et al 2015a). Interestingly, several recent studies demonstrated that populations closely related to those obtained from parasitic populations thriving within the leaves of A. vulgare also occur in various subaerial microhabitats throughout Europe as free-living microalgae (Cutler et al 2013, Hallmann et al 2013, Procházková et al 2015a.…”