Abstract
Cactaceae comprise a diverse and iconic group of flowering plants which are almost exclusively indigenous to the New World. The wide variety of growth forms found amongst the cacti have led to the trafficking of many species throughout the world as ornamentals. Despite the evolution and physiological properties of these plants having been extensively studied, little research has focused on cactus-associated viral communities. While only single-stranded RNA viruses had ever been reported in cacti, here we report the discovery of cactus-infecting single-stranded DNA viruses. These viruses all apparently belong to a single divergent species of the family Geminiviridae and have been tentatively named Opuntia virus 1 (OpV1). A total of 79 apparently complete OpV1 genomes were recovered from 31 different cactus plants (belonging to 20 different cactus species from both the Cactoideae and Opuntioideae clades) and from nine cactus-feeding cochineal insects (Dactylopius sp.) sampled in the USA and Mexico. These 79 OpV1 genomes all share > 78.4% nucleotide identity with one another and < 64.9% identity with previously characterized geminiviruses. Collectively, the OpV1 genomes display evidence of frequent recombination, with some genomes displaying up to five recombinant regions. In one case, recombinant regions span ~40% of the genome. We demonstrate that an infectious clone of an OpV1 genome can replicate in Nicotiana benthamiana and Opuntia microdasys. In addition to expanding the inventory of viruses that are known to infect cacti, the OpV1 group is so distantly related to other known geminiviruses that it likely represents a new geminivirus genus. It remains to be determined whether, like its cactus hosts, its geographical distribution spans the globe.
Highlights
With the exception of a single species, Rhipsalis baccifera (Sols.) Stearn, which is found in some tropical areas of the Old World, cacti are endemic to the Americas [1]
Based on geminivirus-like contigs recovered from these samples by HTS, a pair of abutting primers (OpV1 F/R) were designed to recover the full-length geminivirus-like genomes
We identified replication-associated iterative sequences “iterons”, the TATA box and conserved late element (CLE)-like sequences (Figure 1)
Summary
With the exception of a single species, Rhipsalis baccifera (Sols.) Stearn, which is found in some tropical areas of the Old World, cacti are endemic to the Americas [1]. Since Europeans first arrived in the Americas, cacti have been transported throughout the world [1]: to be grown primarily as ornamentals, and as a crop for their fruit and stems (known as nopales) and the farming of cochineal insects (Dactylopius spp.), the latter of which are members of the order Hemiptera, used for the production of the carminic acid dye [8]. A handful of viruses have been identified in other members of the Cactaceae, all of which belong to the single-stranded RNA virus families Alphaflexiviridae, Betaflexiviridae, Puribunyaviridae, Tombusviridae and Virgaviridae [10,11,12,13,14,15,16,17,18]. No plant-infecting DNA viruses (i.e., viruses belonging to the families Geminiviridae, Nanoviridae, and Caulimoviridae) have ever been found to infect cacti
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