The Parasitic Plant Genome Project: New Tools for Understanding the Biology ofOrobancheandStriga

Abstract

The Parasitic Plant Genome Project has sequenced transcripts from three parasitic species and a nonparasitic relative in the Orobanchaceae with the goal of understanding genetic changes associated with parasitism. The species studied span the trophic spectrum from free-living nonparasite to obligate holoparasite. Parasitic species used wereTriphysaria versicolor, a photosynthetically competent species that opportunistically parasitizes roots of neighboring plants;Striga hermonthica, a hemiparasite that has an obligate need for a host; andOrobanche aegyptiaca, a holoparasite with absolute nutritional dependence on a host.Lindenbergia philippensisrepresents the closest nonparasite sister group to the parasitic Orobanchaceae and was included for comparative purposes. Tissues for transcriptome sequencing from each plant were gathered to identify expressed genes for key life stages from seed conditioning through anthesis. Two of the species studied,S. hermonthicaandO. aegyptiaca, are economically important weeds and the data generated by this project are expected to aid in research and control of these species and their relatives. The sequences generated through this project will provide an abundant resource of molecular markers for understanding population dynamics, as well as provide insight into the biology of parasitism and advance progress toward understanding parasite virulence and host resistance mechanisms. In addition, the sequences provide important information on target sites for herbicide action or other novel control strategies such as trans-specific gene silencing.

Effect of native Trichoderma viride and Pseudomonas fluorescens on the development of Cuscuta campestris on chickpea, Cicer arietinum

“…As the distance of the Cuscuta from the host plant increases, delays in flowering in Cuscuta also increases linearly. Understanding the process of their parasitization and development would lead to develop efficient strategies for their management (Westwood et al, 2012). Contrast to the earlier reports about physical and physiological dormancy of C. campestris and about a high percentage of newly matured seeds of C. campestris not imbibing water to germinate readily (Hutchison and Ashton, 1980) and the need for acid scarification (Jayasuriya et al, 2008), our studies have proved that fresh seeds, before drying in the plants germinates immediately without any need for scarification.…”

Striga

“…For these poor farmers, millets are the major staple food providing them with carbohydrates and is the main source of vitamins and minerals including zinc and iron, (Andrews and Kumar, 1992;Rai et al, 2012;Bangoura et al, 2011;Mannuramath et al, 2015;Mishra et al, 2014). Hence, yield losses lead to significant negative socioeconomic problems: Striga affects the life of more than 300 million people in Africa and causes economic damage equivalent or even more than US$10 billion annually (Obilana and Ramaiah, 1992;Gurney et al, 2002;Rodenburg et al, 2005;Ejeta, 2007;Scholes and Press, 2008;Westwood et al, 2012). More recently, as a consequence, sub-Saharan Africa has been reported to be the region with the highest prevalence of poverty and undernourishment, with one in four people (24.8%) estimated to be hungry (FAO, IFAD and WFP, 2013).…”

“…However, it can be assumed that such strategies has also evolved to achieve maximal chance of parasitism under various ecological conditions. More recently, the usage of modern omics technologies is expected to shed light on the recent developments in molecular analysis and the need to study the biology of the parasitic plants at the molecular level which will provide insight into the genetic changes associated with parasitism throughout evolution (Westwood et al, 2012).…”

“…Indeed, studies aimed at the molecular characterization of the host plant -parasite interaction and host resistance through expression analysis of the genes, proteins and metabolites involved in these processes, are the subject of increasing interest and offer weed researchers the opportunity for deploying genetic transformation tools to enhance the control of the parasitic plants (Rispail et al, 2007;Aly, 2012). With the great initiative of the parasitic plant genome project' (http://ppgp.huck.psu.edu/) (Westwood et al, 2012), genetic resistance based on silencing of a target gene in the host plant is now feasible. Yoder et al (2009) and Runo et al (2011) have investigated the use of RNA interference (RNAi) technology as a mean for enhancing host resistance against parasitic weeds.…”

“…Crop yield losses due to Striga attacks range from a few percent to complete crop failure and depend largely on the cereal host species and variety grown, rainfall distribution, soil fertility and the Striga seed density in soil Parker and Riches, 1993). The annual yield loss has been estimated to exceed US$10 billion (Gressel et al, 2004;Venne et al, 2009;Westwood et al, 2012;Pennisi, 2015). More recently, S. hermonthica has been identified as one of the seven most severe biological constraints to food production.…”