Control of the Azolla symbiosis sexual reproduction: ferns to shed light on the origin of floral regulation?

ABSTRACTAzolla ferns and the filamentous cyanobacteria Nostoc azollae constitute a model symbiosis that enabled colonization of the water surface with traits highly desirable for development of more sustainable crops: their floating mats capture CO2 and fixate N2 at high rates phototrophically. Their mode of sexual reproduction is heterosporous. Regulation of the transition from vegetative to spore-forming phases in ferns is largely unknown, yet a pre-requisite for Azolla domestication, and of particular interest since ferns represent the sister lineage of seed plants.Far-red light (FR) induced sporocarp formation in A. filiculoides. Sporocarps obtained, when crossed, verified species attribution of Netherlands strains but not Iran’s Anzali lagoon. FR-responsive transcripts included CMADS1 MIKCC-homologues and miRNA-controlled GAMYB transcription factors in the fern, transporters in N.azollae, and ycf2 in chloroplasts. Loci of conserved miRNA in the fern lineage included miR172, yet FR only induced miR529 and miR535, and reduced miR319 and miR159.Suppression of sexual reproduction in both gametophyte and sporophyte-dominated plant lineages by red light is likely a convergent ecological strategy in open fields as the active control networks in the different lineages differ. MIKCC transcription factor control of flowering and flower organ specification, however, likely originated from the diploid to haploid phase transition in the homosporous common ancestor of ferns and seed plants.

Taxonomical and functional diversity of Saprolegniales in Anzali lagoon, Iran

Studies on the diversity, distribution and ecological role of Saprolegniales (Oomycota) in freshwater ecosystems are currently receiving attention due to a greater understanding of their role in carbon cycling in various aquatic ecosystems. In this study, we characterized several Saprolegniales species isolated from Anzali lagoon, Gilan province, Iran, using morphological and molecular methods. Four species of Saprolegnia were identified, including S. anisospora and S. diclina as first reports for Iran. Evaluation of the ligno-, cellulo- and chitinolytic activities were also measured using plate assay methods. Most of the Saprolegniales isolates were obtained in autumn and nearly 50% of the strains showed chitinolytic and cellulolytic activities. However, only a few Saprolegniales strains showed lignolytic activities. This study has important implications for better understanding the ecological niche of oomycetes, and to differentiate them from morphologically similar but functional different aquatic fungi in freshwater ecosystems.