The Transcriptome Of The Fungus Fibulorhizoctonia Sp.and The Relationship Between Reticulitermes Labralis And Fibulorhizoctonia Sp.

Insects and fungi share a close relationship in the evolution.In this study,we reported a brown ball found in the piles of eggs of the Reticulitermes labralis(Hsia).Morphology and rDNA analysis identified the ball as the sclerotia of the fungus,Fibulorhizoctonia sp..Sclerotia were spherical brown balls with 0.30-0.40mm in diameter.The fungal sclerotium was a tough ball of densely packed filaments whose growth pattern was the spread of radial.Nowadays little is known about the fungal sclerotia of Fibulorhizoctonia sp..In the present study,we tested whether workers could recognize eggs and sclerotia.Meanwhile,we used behavior observation and the transcriptome of the fungus Fibulorhizoctonia sp.to study the relationship between the termite,R.labralis,and Fibulorhizoctonia sp..Workers could ingest the filaments to obtain extra cellulase and energy.The results were showed as following:1.30 sclerotia were arranged in the nests of four species of termite in Reticulitermes,behavior observation implied that three species of termite R.labralis?R.flavicep and R.chinensis)could recognize the fungal sclerotia and carry them into their egg piles,except the R.aculabialis.When the sclerotia were placed together with eggs,workers carried eggs firstly from those objects.The results showed that workers of R.labralis could distinguish the sclerotia from their eggs.2.The sclerotium with densely filaments could germinate into a fungal colony under favourable conditions without termites,however,we didn't observe the sclerotial germination in the nest of R.labralis.The color of those sclerotia in the nest of R.labralis changed into dark brown,and the number decreased gradually.We inferred that the filaments were ingested by workers.3.The transcriptome of the sclerotia of Fiblorhizoctonia sp.was sequenced and analyzed.A total of 33,612,236 reads were obtained via Hi-SeqTM 4000(Illumina)paired-end sequencing.The sample generated 6G of transcriptome data.After trimming the raw reads,there were 31,412,704 clean reads remaining.Based on the clean reads,a total of 28,026 unigenes ranging from 201 to 13,121bp were assembled with Trinity software.The average length was 998 bp and the N50 was 1,647 bp.The Q20 value was 96.9%and the sample GC content was 53.57%.Analyses showed that 3,976 unigenes could be annotated in one or more databases.17,291 unigenes had significant matches in the NR database.8,959 unigenes had significant matches in the Swiss-Prot database.7,407 unigenes had significant matches in the KOG database.4,990 unigenes had significant matches in the KEGG database.It was the first time to complish the RNA sequencing of Fibulorhizoctonia sp..The remaining 10,627 unigenes that lacked annotation information could not be matched to known genes.These unigenes would also be specific genes of Fibulorhizoctonia sp.4.The qRT-PCR was used to detect the relative expression level of cellulase.There were 12 cellulase genes in Fibulorhizoctonia sp.,that is,five(3-glucosidase genes,four endo-beta-1,4-glucanase genes and three exo-beta-1,4-glucanase genes.Meanwhile,we demonstrated that there was no significant difference in the expression level of?-glucosidase(l)between R.labralis and R.aculabialis;the relative expression level of?-glucosidase(2)of R.labralis was 1.4-fold higher than that of R.aculabialis;the relative expression level of endoglucanase of R.labralis was 1.9-fold higher than that of R.aculabialis.The comparative studies based on cellulase in different species of termite were likely to reveal the different reactions on sclerotia.The different expression levels of cellulase genes might be related to the cellulose degradation efficiency.We inferred that R.labralis is better than R.aculabialis in the synthesis of cellulase,which may directly affect their differences in individual development and reproductive ability.