Developmental Transcript Profiling of Cyst Nematode Feeding Cells in Soybean Roots

Abstract

Cyst nematodes of the genus Heterodera are obligate, sedentary endoparasites that have developed highly evolved relationships with specific host plant species. Successful parasitism involves significant physiological and morphological changes to plant root cells for the formation of specialized feeding cells called syncytia. To better understand the molecular mechanisms that lead to the development of nematode feeding cells, transcript profiling was conducted on developing syncytia induced by the soybean cyst nematode Heterodera glycines in soybean roots by coupling laser capture microdissection with high-density oligonucleotide microarray analysis. This approach has identified pathways that may play intrinsic roles in syncytium induction, formation, and function. Our data suggest interplay among phytohormones that likely regulates synchronized changes in the expression of genes encoding cell-wall-modifying proteins. This process appears to be tightly controlled and coordinately regulated with cell wall rigidification processes that may involve lignification of feeding cell walls. Our data also show local downregulation of jasmonic acid biosynthesis and responses in developing syncytia, which suggest a local suppression of plant defense mechanisms. Moreover, we identified genes encoding putative transcription factors and components of signal transduction pathways that may be important in the regulatory processes governing syncytium formation and function. Our analysis provides a broad mechanistic picture that forms the basis for future hypothesis-driven research to understand cyst nematode parasitism and to develop effective management tools against these pathogens.

Manipulation of Auxin Transport in Plant Roots during Rhizobium Symbiosis and Nematode Parasitism

“…The impressive transformation of the plant cell infected by sedentary endoparasitic nematodes goes along with a plethora of physiological and molecular changes (Jammes et al, 2005;Ithal et al, 2007;Gheysen and Mitchum, 2009). Similar to nodule initiation, an enhanced auxin response has been visualized at the infection sites of both cyst and root-knot nematodes, whereas auxin signaling mutants have shown significantly lower nematode infection (Hutangura et al, 1999;Goverse et al, 2000;Karczmarek et al, 2004;Grunewald et al, 2008).…”

Application of Laser Microdissection to plant pathogenic and symbiotic interactions

“…On the other side, precipitative fixatives, such as Farmer's fixative (ethanol/glacial acetic acid 3:1), are simple to make and provide both sample histological detail of plant tissues and enough RNA recovery for the downstream molecular analyses. RNA extracted from microdissected cells collected from plant tissues fixed with this method has been successfully used for molecular analyses (Kerk et al 2003;Nakazono et al 2003;Ramsay et al 2004;Klink et al 2005Klink et al , 2007aIthal et al 2007). A fixative that leads to a good balance between tissue preservation versus RNA recovery is a solution known as methacarn, which consists of absolute methanolchloroform-glacial acetic acid (6:3:1; Takagi et al 2004;Jiang et al 2006;Balestrini et al 2007;Guether et al 2009).…”

“…An important aspect of most LM-mediated gene expression research is that the RNA usually has to be amplified in order to obtain a sufficient amount of sample for the desired work. RNA yield obtained from microdissected cells is in fact generally enough for targeted molecular analysis like RT-PCR, while one or two rounds of RNA amplification are required to obtain the microgram amounts of mRNA needed for global profiling analyses (Nakazono et al 2003;Klink et al 2007a;Ithal et al 2007). Several methods and commercial kits for RNA amplification, that maintain the relative representation of RNA species, have been developed and can be used specifically for this purpose (Brandt 2005).…”

“…This allows researchers to carry out spatial and temporal gene expression profiling (Day et al 2005). These sorts of projects include investigations of the gene expression that occur during the interaction between plants and nematodes (Ramsay et al 2004;Klink et al 2005Klink et al , 2007aIthal et al 2007), fungal pathogen (Tang et al 2006) and arbuscular mycorrhizal (AM) fungi Guether et al 2009; (Table 1). Each of these studies, which so far have been performed in the field of plant/microbe interactions, employs an embedding step followed by serial sectioning of the tissue since the cells are located deep within the root tissue.…”

“…An area of interest is the development and maintenance of nematode feeding sites. LM methods that faithfully dissect out the feeding sites are important improvements to the study of this significant plant-pathogen interaction (Ramsay et al 2004;Klink et al 2005Klink et al , 2007aIthal et al 2007;Klink and Matthews 2008).…”