De Novo Assembly and Characterization of the Transcriptome of the Parasitic Weed Dodder Identifies Genes Associated with Plant Parasitism      

Abstract

Parasitic flowering plants are one of the most destructive agricultural pests and have major impact on crop yields throughout the world. Being dependent on finding a host plant for growth, parasitic plants penetrate their host using specialized organs called haustoria. Haustoria establish vascular connections with the host, which enable the parasite to steal nutrients and water. The underlying molecular and developmental basis of parasitism by plants is largely unknown. In order to investigate the process of parasitism, RNAs from different stages (i.e. seed, seedling, vegetative strand, prehaustoria, haustoria, and flower) were used to de novo assemble and annotate the transcriptome of the obligate plant stem parasite dodder (Cuscuta pentagona). The assembled transcriptome was used to dissect transcriptional dynamics during dodder development and parasitism and identified key gene categories involved in the process of plant parasitism. Host plant infection is accompanied by increased expression of parasite genes underlying transport and transporter categories, response to stress and stimuli, as well as genes encoding enzymes involved in cell wall modifications. By contrast, expression of photosynthetic genes is decreased in the dodder infective stages compared with normal stem. In addition, genes relating to biosynthesis, transport, and response of phytohormones, such as auxin, gibberellins, and strigolactone, were differentially expressed in the dodder infective stages compared with stems and seedlings. This analysis sheds light on the transcriptional changes that accompany plant parasitism and will aid in identifying potential gene targets for use in controlling the infestation of crops by parasitic weeds.

Local Auxin Biosynthesis Mediated by a YUCCA Flavin Monooxygenase Regulates Haustorium Development in the Parasitic Plant Phtheirospermum japonicum

“…The currently available EST sequences in parasitic plants are still limited to several species; ESTs for three members of the Orobanchaceae family, i.e., S. hermonthica, P. aegyptiaca, and T. versicolor (Yoshida et al, 2010;Yang et al, 2014), the root parasite in Santalales, S. album (sandalwood), and the stem parasite Cuscuta pentagona (Kim et al, 2014;Ranjan et al, 2014) have been reported. The P. japonicum sequences analyzed in this study provide a valuable addition to parasitic plant gene databases and are suitable for conducting comparative analyses with other parasitic species.…”

Overexpression of stress-related genes in Cuscuta campestris in response to host defense reactions

“…Those genes have also been implicated in stress responses. Comparative transcriptomic analysis such as cDNA-AFLP provided a valuable resource for studying host-dodder interactions in the past (Ranjan et al, 2014;Breyne and Zabeau, 2001). In our research, the highest upregulation in cDNA-AFLP analysis was observed for genes encoding for heme-binding protein, lysine-specific demethylase, and ATP-dependent RNA helicase.…”

“…Defense mechanisms may be induced by dodder parasitism in the host plants (Runyon et al, 2010). Interestingly, the parasitic plant is also under biotic stress and uses its own defense mechanisms to overcome the host's counter attack (Ranjan et al, 2014). Some stress conditions modulate heme synthesis (DeFranceschi et al, 2011); similarly to other heme-binding proteins, it may be involved in the cellular protection against heme-mediated oxidative damage to the cell (Immenschuh et al, 1999).…”

“…Cuscutain (a cysteine protease from Cuscuta reflexa ) playing a role in host-parasite interactions (Bleischwitz et al, 2010), genes encoding enzymes involved in cell wall modifications (Ranjan et al, 2014) taking part in haustorium development have been identified as well. Jiang et al, (2013) discovered ESTs (Expressed Sequence Tags) with sequence similarities to known plant viruses, including cryptic viruses, in the dodder sequence assemblies.…”

Genetics and Genomics of Cultivated Eggplants and Wild Relatives

“…This huge set of non-annotated short sequences has been observed in recent published transcriptomes, in which large amount of raw reads have been obtained (Ranjan et al, 2014;Zhang J et al, 2015).…”