Basal repertoire of toxin-related transcripts in the zoanthid Protopalythoa variabilis(Cnidaria,Anthozoa)

OBJECTIVE To analyze the whole transcriptome of zoanthid Protopalythoa variabilis(P.variabilis),a cnidarian,and discover the potential toxic substances in P.variabilis.METHODS The P.variabilis RNA deep sequencing was performed using the HiSeq 2500 automatic sequencing platform.All the unigenes generated from the assembly process were functionally annotated based on the similarity with databases.The multiple alignments of translated toxin-related sequences were performed with Clustalw2,and amino acid identity and similarity highlighted by using BoxShade tool.Three different methods including ITASSER,PEP-FOLD and MODELLER were applied to predict tri-dimensional models of toxin-related polypeptides from translated transcript sequences of P.variabilis.The toxicity of one of the putative toxins,namely ShK/Aurelin-like peptide,was evaluated using zebrafish model.RESULTS A total of 67,549,914 pairs of quality-filtered,90-base-pair Illumina reads from an mRNA sample were obtained.The de novo assemblies yielded 276,526 contigs.The sequence comparison of 130,121 unigenes with entries in Toxin database showed that 1542 unigenes were potential peptide toxins at which 11 unigenes were related to Stichodactyla toxin(ShK)domain(Pfam ID:PF01549).ShK is a 35 residues peptide sequence that was firstly discovered from the sea anemone Stichodactyla helianthus.Here,we found out one ShK-like peptide that processed a relatively higher sequence similarity with known ShK(Uniprot ID:P29186)of Bunodosoma granuliferum(red warty sea anemone).The Protopalythoa Shk-like peptide was submitted to Probis server to detect probable binding site and found to match with a protein AURELIN(PDB id:2lg4,UniProt id:Q0MWV8)which possesses structural homology with previously identified antimicrobial peptides and K+-channel-blocking toxins.Our results showed that the ShK/Aurelin-like peptide was lethal to zebrafish embryos at concentrations above 30-μmol·L1,and could induce zebrafish locomotor deficit at 10μmol·L-1.CONCLUSION This study,for the first time,presented the whole transcriptome profile and a potential toxic peptide of P.variabilis.

Dynamics in the emergence of dormant and non-dormant herbaceous species from the soil seed bank from a Brazilian dry forest

Aims In dry tropical forests,herbaceous species may have dormancy mechanisms and form persistent and transient seed banks in the soil.Evolutionarily acquired,these mechanisms are efficient for the establishment and survival of these herbs,especially in forests with unpredictable climates,such as the Caatinga.Thus,our objective was to verify whether the studied herbaceous species adopt the physical dormancy mechanism and how these natural barriers are overcome,to understand the temporal dynamics existing in the soil seed bank from a Brazilian dry tropical forest.Methods Seeds of five native herbaceous species from the Caatinga forests were selected and submitted to pre-germinative treatments for verifying the presence of physical dormancy.We collected soil samples in the rainy and dry seasons for four consecutive years and monitored the emergence of the selected herbaceous in the greenhouse.We verified the differences in germination and seed bank emergence in the soil by generalized linear models.Important Findings The presence and absence of physical dormancy were observed in seeds from Caatinga herbaceous species.We found intraspecific and interspecific differences in the herbaceous emergence from soil seed banks between years and climatic seasons.In perennial herbs,consecutive lack of emergence between seasons and years was frequent,which suggests a direct relationship with the mechanism of physical dormancy and the environmental conditions necessary to overcome integument barriers.In these species,seed dimorphism and dormancy may confer additional advantages to their survival.Moreover,presenting intermediate levels of physical dormancy in an annual species may be an evolutionary adjustment to rainfall unpredictability.In contrast,we found that the annual herb without dormancy is more sensitive to seasonal and interannual climate changes,as evidenced by the increase and significant reduction of its emergence in the soil seed bank.These differences acquired evolutionarily are advantageous for the establishment of herbaceous populations,mainly in semiarid regions with an unpredictable climate.