Complete genome sequence of a new strain of Lagenaria siceraria endornavirus from China

Four closely related endornaviruses each with a low incidence in the phytopathogenic fungi Exserohilum turcicum or Bipolaris maydis

Endornaviruses are known to occur widely in plants, fungi, and oomycetes, but our understanding of their diversity and distribution is limited. In this study, we report the discovery of four endornaviruses tentatively named Setosphaeria turcica endornavirus 1 (StEV1), Setosphaeria turcica endornavirus 2 (StEV2), Bipolaris maydis endornavirus 1 (BmEV1), and Bipolaris maydis endornavirus 2 (BmEV2). StEV1 and StEV2 infect Exserohilum turcicum, while BmEV1 and BmEV2 infect Bipolaris maydis. The four viruses encode a polyprotein with less than 40 % amino acid sequence identity to other known endornaviruses, indicating that they are novel, previously undescribed endornaviruses. However, StEV1 and BmEV1 share a sequence identity of 78 % at the full-genome level and 87 % at the polyprotein level, suggesting that they may belong to the same species. Our study also found that each of the four endornaviruses has an incidence of approximately 3.5 % to 5.5 % in E. turcicum or B. maydis. Interestingly, BmEV1 and BmEV2 were found to be unable to transmit between hosts of different vegetative incompatibility groups, which may explain their low incidence.

Identification of a novel alphaendornavirus from Lonicera maackii

A new alphaendornavirus, tentatively named "Lonicera maackii alphaendornavirus" (LmEV), was identified in a Lonicera maackii plant in Beijing, China, with leaf abnormality of interveinal chlorosis, and its complete genome sequence was determined using small-RNA deep sequencing. The RNA genome of LmEV is 16,176 nt in length and contains a large open reading frame encoding a polyprotein of 5363 aa with conserved domains including a cysteine-rich region, a viral helicase, and an RNA-dependent RNA polymerase. Sequence comparisons showed that LmEV shared the highest nt and aa sequence identity with Vicia faba alphaendornavirus (VfEV) of the genus Alphaendornavirus. In phylogenetic analysis of the RdRp aa sequence LmEV clustered with members of the genus Alphaendornavirus, closest to VfEV. To our knowledge, this is the first report of a novel alphaendornavirus identified in Lonicera maackii. Its effect on the host plant, if any, remains to be investigated.

A high-quality sponge gourd (Luffa cylindrica) genome

Sponge gourd (Luffa cylindrica) is an important cultivated vegetable and medicinal plant in the family Cucurbitaceae. In this study, a draft genome sequence of the sponge gourd inbred line P93075 was analyzed. Using Illumina, PacBio, and 10× Genomics sequencing techniques as well as new assembly techniques such as FALCON and chromatin interaction mapping (Hi-C), a chromosome-scale genome of approximately 656.19 Mb, with an N50 scaffold length of 48.76 Mb, was generated. From this assembly, 25,508 protein-coding gene loci were identified, and 63.81% of the whole-genome consisted of transposable elements, which are major contributors to the expansion of the sponge gourd genome. According to a phylogenetic analysis of conserved genes, the sponge gourd lineage diverged from the bitter gourd lineage approximately 41.6 million years ago. Additionally, many genes that respond to biotic and abiotic stresses were found to be lineage specific or expanded in the sponge gourd genome, as demonstrated by the presence of 462 NBS-LRR genes, a much greater number than are found in the genomes of other cucurbit species; these results are consistent with the high stress resistance of sponge gourd. Collectively, our study provides insights into genome evolution and serves as a valuable reference for the genetic improvement of sponge gourd.

Complete sequence of a novel alphaendornavirus from the phytopathogenic fungus Arthrocladiella mougeotii

A novel double-stranded RNA (dsRNA) virus, which was provisionally named Arthrocladiella mougeotii endornavirus (AmEV), was isolated from Arthrocladiella mougeotii, the phytopathogenic fungus infecting Lycium chinense in Beijing, China. The genome of AmEV is 11,683 nucleotides in length with a 5' and 3' non-coding region of 16 and 50 nt, respectively, as well as a single 11,617-nt long open reading frame potentially encoding a putative protein of 3,871 amino acids with conserved Helicase and RNA-dependent RNA polymerase (RdRp) domains. Phylogenetic analysis based on the the amino acid sequence of the RdRp showed that AmEV is most closely related to Erysiphe cichoracearum endornavirus (EcEV).

The complete genomic sequence of a novel botybirnavirus isolated from a phytopathogenic Bipolaris maydis

Bipolaris maydis is the causal agent of corn southern leaf blight. Here, we report a novel double-stranded RNA (dsRNA) mycovirus designated Bipolaris maydis botybirnavirus 1 (BmBRV1) from B. maydis strain JZ11 in Jingzhou, Hubei province of China. BmBRV1 has a genome consisting of two dsRNAs (dsRNA1 and dsRNA2) with a size of 6435 and 5987 bp, respectively, each of which contains a single open reading frame (ORF). The two polyproteins encoded by dsRNA1 and dsRNA2 share the highest amino acid identities of 81.8 and 75.3%, respectively, with the RdRp and coat protein of Sclerotinia sclerotiorum botybirnavirus 1 (SsBRV1), a tentative species of the genus Botybirnavirus. Phylogenetic analysis based on the amino acid sequences of RdRp indicated that BmBRV1 belongs to a distinct species of the newly proposed family Botybirnaviridae.