Guanchochroma wildpretii gen. et spec. nov. (Ochrophyta) Provides New Insights into the Diversification and Evolution of the Algal Class Synchromophyceae.

A new relative of the chrysophyte genus Chrysopodocystis was found in Tenerife and termed Guanchochroma wildpretii. This unicellular alga was most noticeably discernible from Chrysopodocystis socialis (the only species of this genus) by the presence of a cyst-like stage with a multilayered lorica, which also functions as a dispersal unit and shows secondary wall growth. Secondary expansion of loricae (cell casings not involved in cell division, usually with a more or less pronounced opening) has never been observed previously and marks a unique feature of the new taxon. Plastids are non-randomly distributed within cells of G. wildpretii. 18S rRNA gene analyses identified the two species as sister lineages and placed them in a monophyletic group with the Synchromophyceae, a heterokont algal (Ochrophyta) class characterized by the presence of chloroplast complexes. Yet, neither Chrysopodocystis nor Guanchochroma showed this feature in ultrastructure analyses. Additionally, their 18S rRNA genes possessed distinct inserts, the highest GC-content known for Ochrophyta and exceptionally long branches on the Ochrophyta 18S rDNA phylogenetic tree, suggesting substantially increased substitution rates along their branch compared to Synchromophyceae. Plastid marker data (rbcL) recovered a monophyletic clade of Chrysopodocystis, Guanchochroma and Synchromophyceae as well, yet with lower supports for internal split order due to limited resolution of the marker. Evidence for the sequence of events leading to the formation of the plastid complex of Synchromophyceae still remains ambiguous because of the apparently short timeframe in which they occurred.

The compromised recognition of turnip crinkle virus1 subfamily of microrchidia ATPases regulates disease resistance in barley to biotrophic and necrotrophic pathogens.

MORC1 and MORC2, two of the seven members of the Arabidopsis (Arabidopsis thaliana) Compromised Recognition of Turnip Crinkle Virus1 subfamily of microrchidia Gyrase, Heat Shock Protein90, Histidine Kinase, MutL (GHKL) ATPases, were previously shown to be required in multiple layers of plant immunity. Here, we show that the barley (Hordeum vulgare) MORCs also are involved in disease resistance. Genome-wide analyses identified five MORCs that are 37% to 48% identical on the protein level to AtMORC1. Unexpectedly, and in clear contrast to Arabidopsis, RNA interference-mediated knockdown of MORC in barley resulted in enhanced basal resistance and effector-triggered, powdery mildew resistance locus A12-mediated resistance against the biotrophic powdery mildew fungus (Blumeria graminis f. sp. hordei), while MORC overexpression decreased resistance. Moreover, barley knockdown mutants also showed higher resistance to Fusarium graminearum. Barley MORCs, like their Arabidopsis homologs, contain the highly conserved GHKL ATPase and S5 domains, which identify them as members of the MORC superfamily. Like AtMORC1, barley MORC1 (HvMORC1) binds DNA and has Mn2+-dependent endonuclease activities, suggesting that the contrasting function of MORC1 homologs in barley versus Arabidopsis is not due to differences in their enzyme activities. In contrast to AtMORCs, which are involved in silencing of transposons that are largely restricted to pericentromeric regions, barley MORC mutants did not show a loss-of-transposon silencing regardless of their genomic location. Reciprocal overexpression of MORC1 homologs in barley and Arabidopsis showed that AtMORC1 and HvMORC1 could not restore each other's function. Together, these results suggest that MORC proteins function as modulators of immunity, which can act negatively (barley) or positively (Arabidopsis) dependent on the species.