Plant Molecular Virology

The research in my laboratory has both an applied aspect and a basic aspect. The main emphasis of the applied research is to incorporate viral resistance genes into crops important to south Texas agriculture using transgenic plant technologies. We have used pathogen derived resistance approaches to create transgenic citrus and sugarcane plants that are resistant to the main viruses causing economic losses in these crops. We are also expressing novel lectins and lytic proteins in transgenic plants for the control of insect viral vectors and phytopathogenic bacteria. Currently, there are projects in both sugarcane and citrus.

In addition to using pathogen derived resistance approaches to create transgenic citrus resistant to Citrus tristeza virus, the most important virus of citrus worldwide, we are developing and utilizing positional cloning methods to isolate viral resistance genes from citrus and citrus relatives. A major effort in the lab has an overall objective to use positional cloning methods to isolate a dominant gene (Ctv) from the trifoliate orange that causes resistance to all know isolates of Citrus tristeza virus. Starting with a genetic linkage map spanning 1.8 cM, and a subsequent chromosome walk of 1.2 Mb, we have narrowed down the genomic region that must contain Ctv to 125 kb, which contains eight candidate genes.

Another major emphasis in the lab is to identify and characterize host proteins involved in the dsRNA mediated antiviral defense pathway. Many different plant viral proteins have been identified as suppressors of this RNA silencing defense pathway. We have identified and are using suppressors encoded by sugarcane viruses as molecular probes to isolate plant proteins in the RNA silencing pathway. To date, five different proteins (including a protein able to bind RNA) have been isolated. Furthermore, using newly developed in vivo assays we have confirmed that the host RNA binding protein and a interacting host 14-3-3 protein are required for RNA silencing. This approach will allow us to dissect this very important RNA surveillance, targeting, and degradation pathway.

Curtis IS, Mirkov TE. (2012). Influence of surfactants on growth and regeneration from mature internodal stem segments of sweet orange (Citrus sinensis) cv. Hamlin. Plant Cell, Tissue and Organ Culture. 108: 345-352.

Mendes S, Moraes AP, Mirkov TE, Pedrosa-Harand A. (2011). Chromosome homeologies and high variation in heterochromatin distribution between Citrus L. and Poncirus Raf. as evidenced by comparative cytogenetic mapping.Chromosome Res. 19: 521-30.

da Costa Silva S, Marques A, dos Santos Soares Filho W, Mirkov TE,  Pedrosa-Harand A. (2011). The Cytogenetic Map of the Poncirus trifoliata (L.) Raf. A Nomenclature System for Chromosomes of All Citric Species. Tropical Plant Biology 4: 99-105.

Beyene G, Buenrostro-Nava MT, Damaj MB, Gao SJ, Molina J, Mirkov TE.(2011).Unprecedented enhancement of transient gene expression from minimal cassettes using a double terminator. Plant Cell Rep. 30: 13-25.

Damaj MB, Beremand PD, Buenrostro-Nava MT, Ivy J, Kumpatla SP, Jifon J, Beyene G, Yu Q, Thomas TL, Mirkov TE. (2010). Isolating promoters of multigene family members from the polyploid sugarcane genome by PCR-based walking in BAC DNA. Genome. 53: 840-7.

Damaj MB, Kumpatla SP, Emani C, Beremand PD, Reddy AS, Rathore KS, Buenrostro-Nava MT, Curtis IS, Thomas TL, Mirkov TE. (2010). Sugarcane DIRIGENT and O-methyltransferase promoters confer stem-regulated gene expression in diverse monocots. Planta. 231: 1439-58.

Mangwende T, Wang ML, Borth W, Hu J, Moore PH, Mirkov TE, Albert HH. (2009).The P0 gene of Sugarcane yellow leaf virus encodes an RNA silencing suppressor with unique activities. Virology. 384: 38-50.

Moraes AP, Mirkov TE, Guerra M. (2008). Mapping the chromosomes of Poncirus trifoliata Raf. by BAC-FISH. Cytogenet Genome Res. 121: 277-81.

Xu DL, Park JW, Mirkov TE, Zhou GH. (2008). Viruses causing mosaic disease in sugarcane and their genetic diversity in southern China. Arch Virol. 153: 1031-9.