A new genus of alphasatellites associated with banana bunchy top virus in Southeast Asia.

Autonomously replicating alphasatellites (family Alphasatellitidae) are frequently associated with plant single-stranded (ss)DNA viruses of the families Geminiviridae, Metaxyviridae, and Nanoviridae. Alphasatellites encode a single replication-initiator protein (Rep) similar to Rep proteins of helper viruses and depend on helper viruses for encapsidation, movement, and transmission. Costs versus benefits of alphasatellite-helper virus association are poorly understood. Our surveys in Southeast Asia (SEA) for wild and cultivated banana plants infected with banana bunchy top virus (BBTV, Nanoviridae) and Illumina sequencing reconstruction of their viromes revealed, in addition to a six-component BBTV genome, one to three distinct alphasatellites present in sixteen of twenty-four BBTV-infected plants. Comparative nucleotide and Rep protein sequence analyses classified these alphasatellites into four distinct species: two known species falling into the genus Muscarsatellite (subfamily Petromoalphasatellitinae) previously identified in SEA and two novel species falling into the tentative genus Banaphisatellite (subfamily Nanoalphasatellitinae) so far containing a single species recently identified in Africa. The banaphisatellites were found to be most related to members of the genus Fabenesatellite of subfamily Nanoalphasatellitinae and the genus Gosmusatellite of subfamily Geminialphasatellitinae, both infecting dicots. This suggests a dicot origin of banaphisatellites that got independently associated with distinct strains of monocot-infecting BBTV in Africa and SEA. Analysis of conserved sequence motifs in the common regions driving replication and gene expression of alphasatellites and BBTV strains revealed both differences and similarities, pointing at their ongoing co-evolution. An impact of alphasatellites on BBTV infection and evasion of RNA interference-based antiviral defences was evaluated by measuring relative abundance of BBTV genome components and alphasatellites and by profiling BBTV- and alphasatellite-derived small interfering RNAs. Taken together, our findings shed new light on the provenance of alphasatellites, their co-evolution with helper viruses, and potential mutual benefits of their association.

Evidence for Dicot Plants as Alternative Hosts of Banana Bunchy Top Virus and Its Alphasatellites in South-East Asia.

Banana bunchy top virus is a multicomponent circular ssDNA virus (family Nanoviridae) that causes one of the most devastating diseases of cultivated bananas and plantains (family Musaceae). It is transmitted by the aphids Pentalonia nigronervosa and P. caladii among host plants of Musaceae and some other families of monocots. Our Illumina sequencing reconstruction of virome components of BBTV-infected banana plants and their neighbor non-banana plants sampled in Vietnam and Laos revealed the monocot Commelina sp. (Commelinaceae) and the dicots Bidens pilosa and Chromolaena odorata (both Asteraceae) as hosts of BBTV and circular ssDNA alphasatellites (family Alphasatellitidae). Counting the proportions and relative abundances of Illumina reads representing BBTV genome components and alphasatellites suggested that Chromolaena and Commelina are poor hosts for BBTV and one to three alphasatellite species, whereas Bidens is a permissive host for BBTV and four alphasatellite species representing two genera of Alphasatellitidae. Our findings provide evidence for the dicot plants of family Asteraceae as alternative hosts of BBTV and its alphasatellites, which warrants further investigation of these and other dicots as a potential refuge and source of BBTV and multiple alphasatellites that become associated with this virus and likely affect its replication, transmission, and host range.

Typification of names in Kaempferia (Zingiberaceae) in the flora of Cambodia, Laos and Vietnam.

Neotypes are designated for five names in Kaempferia (Zingiberaceae) from Lao PDR, namely K.attapeuensis Picheans. & Koonterm, K.champasakensis Picheans. & Koonterm, K.gigantiphylla Picheans. & Koonterm, K.sawanensis Picheans. & Koonterm and K.xiengkhouangensis Picheans. & Phokham.