Genetic diversity and population structure of Camellia huana (Theaceae), a limestone species with narrow geographic range, based on chloroplast DNA sequence and microsatellite markers

Camellia huana is an endangered species with a narrow distribution in limestone hills of northern Guangxi and southern Guizhou provinces, China. We used one chloroplast DNA (cpDNA) fragment and 12 pairs of microsatellite (simple sequence repeat; SSR) markers to assess the genetic diversity and structure of 12 C. huana populations. A total of 99 alleles were detected for 12 polymorphic loci, and eight haplotypes and nine polymorphic sites were detected within 5200 bp of cpDNA. C. huana populations showed a low level of genetic diversity (n = 8, Hd = 0.759, Pi = 0.00042 for cpDNA, N _A  = 3.931, H _E  = 0.466 for SSRs), but high genetic differentiation between populations (F _ST  = 0.2159 for SSRs, F _ST  = 0.9318 for cpDNA). This can be attributed to the narrow distribution and limestone habitat of C. huana. STRUCTURE analysis divided natural C. huana populations into two groups, consistent with their geographical distribution. Thus, we suggest that five natural C. huana populations should be split into two units to be managed effectively.

Functional redundancy in Echinocandin B in-cluster transcription factor ecdB of Emericella rugulosa NRRL 11440

Echinocandin B is a potent antifungal against the majority of fungal pathogens and its biosynthesis occurred by ecd and hty gene clusters in Emericella rugulosa NRRL 11440. We elucidated the functional necessity of in-clustered transcription factor; ecdB in the production of echinocandin B. We deleted the ecdB gene and found that ΔecdB mutant has no significant effect on echinocandin B production. The expression level of most of the ecd and hty cluster genes was not significantly altered except few of them up-regulated in knockout strain. The complete abrogation in ecdB gene expression was observed in ΔecdB strain. However, the interactions of purified EcdB protein with DNA sequence of ecdA, ecdH, ecdK and ecdI promoter was confirmed in-vitro. Our results conclude that EcdB protein in-vitro binds to the ecdA, ecdH, ecdK and ecdI promoter but in-vivo, it could not significantly affect the gene expression and echinocandin B production in Emericella rugulosa.