Spatial profiling of maytansine during the germination process of Maytenus senegalensis seeds.

The ecological role of maytansine, an important antineoplastic and antimicrobial compound with high cytotoxicity, particularly as a chemical defense compound has remained elusive since its discovery in the 1970s in Maytenus and Putterlickia plants. In the present study, we have used MALDI-imaging-HRMS to visualize the occurrence as well as spatial and temporal distribution of maytansine in a Maytenus senegalensis plant, seeds obtained from the mother plant during seeding stage, through the germination of the seeds, and finally up to the establishment of seedlings (or daughter plants). Although the mother plant was devoid of maytansine, the bioactive compound was found to be distributed in the cotyledons and the endosperm of the seeds with an augmented accretion towards the seed coat. Furthermore, maytansine was always detected in the emerging seedlings, particularly the cortex encompassing the radicle, hypocotyl, and epicotyl. The typical pattern of accumulation of maytansine not only in the seeds but also during germination provides a proof-of-concept that M. senegalensis is ecologically primed to trigger the production of maytansine in vulnerable tissues such as seeds during plant reproduction. By utilizing maytansine as chemical defense compound against predators and/or pathogens, the plant can ensure viability of the seeds and successful germination, thus leading to the next generation of daughter plants.

Pseudonocardia tropica sp. nov., an endophytic actinomycete isolated from the stem of Maytenus austroyunnanensis.

A novel strain, designated YIM 61452(T), was isolated from the stem of Maytenus austroyunnanensis collected from the tropical rainforest of Xishuangbanna, Yunnan Province, south-west China. The strain was characterized taxonomically by using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain YIM 61452(T) belonged to the genus Pseudonocardia and was most closely related to Pseudonocardia alni IMSNU 20049(T) (99.5 %), Pseudonocardia antarctica DVS 5a1(T) (99.5 %) and Pseudonocardia carboxydivorans Y8(T) (99.4 %). The chemotaxonomic properties of strain YIM 61452(T), for example MK-8(H(4)) as the predominant quinone system and iso-C(16 : 0) and iso-C(16 : 1) H as the major fatty acids, were also consistent with its classification within the genus Pseudonocardia. Strain YIM 61452(T) could be differentiated from closely related species of the genus Pseudonocardia by phenotypic and genotypic analysis. DNA-DNA hybridization experiments between strain YIM 61452(T) and closely related reference strains further confirmed that strain YIM 61452(T) represented a novel taxon of the genus Pseudonocardia. Therefore, strain YIM 61452(T) represents a novel species, for which the name Pseudonocardia tropica sp. nov. is proposed. The type strain is YIM 61452(T) (=DSM 45199(T)=CCTCC AA 208018(T)).

Nonomuraea antimicrobica sp. nov., an endophytic actinomycete isolated from a leaf of Maytenus austroyunnanensis.

A novel actinomycete strain, designated YIM 61105(T), was isolated from a leaf of Maytenus austroyunnanensis from the tropical rainforest in Xishuangbanna, Yunnan Province, south-west China. A 16S rRNA gene sequence analysis revealed that the organism belonged to the phylogenetic cluster of the genus Nonomuraea and was most closely related to Nonomuraea candida HMC10(T) (98.2 %), 'Nonomuraea aegyptia' S136 (97.9 %), Nonomuraea kuesteri GW 14-1925(T) (97.5 %) and Nonomuraea turkmeniaca DSM 43926(T) (97.4 %). The 16S rRNA gene sequence similarities to other Nonomuraea species were less than 97.4 %. The main chemotaxonomic properties of strain YIM 61105(T), such as the principal amino acid of the peptidoglycan, the predominant menaquinone and the polar lipid profile, supported its classification within the genus Nonomuraea. Strain YIM 61105(T) was also readily differentiated from closely related species on the basis of a broad range of phenotypic properties and DNA-DNA hybridization values. Thus, this isolate is considered to represent a novel species of the genus Nonomuraea, for which the name Nonomuraea antimicrobica sp. nov. is proposed. The type strain is YIM 61105(T) (=DSM 45220(T)=CCTCC AA 208016(T)).