Global changes in gene expression during compatible and incompatible interactions of cowpea (Vigna unguiculata L.) with the root parasitic angiosperm Striga gesnerioides

Abstract

BackgroundCowpea, Vigna unguiculata L. Walp., is one of the most important food and forage legumes in the semi-arid tropics. While most domesticated forms of cowpea are susceptible to the root parasitic weed Striga gesnerioides, several cultivars have been identified that show race-specific resistance. Cowpea cultivar B301 contains the RSG3-301 gene for resistance to S. gesnerioides race SG3, but is susceptible to race SG4z. When challenged by SG3, roots of cultivar B301 develop a strong resistance response characterized by a hypersensitive reaction and cell death at the site of parasite attachment. In contrast, no visible response occurs in B301 roots parasitized by SG4z.ResultsGene expression in the roots of the cowpea cultivar B301 during compatible (susceptible) and incompatible (resistant) interactions with S. gesnerioides races SG4z and SG3, respectively, were investigated at the early (6 days post-inoculation (dpi)) and late (13 dpi) stages of the resistance response using a Nimblegen custom design cowpea microarray. A total of 111 genes were differentially expressed in B301 roots at 6 dpi; this number increased to 2102 genes at 13 dpi. At 13 dpi, a total of 1944 genes were differentially expressed during compatible (susceptible) interactions of B301 with SG4z. Genes and pathways involved in signal transduction, programmed cell death and apoptosis, and defense response to biotic and abiotic stress were differentially expressed in the early resistance response; at the later time point, enrichment was primarily for defense-related gene expression, and genes encoding components of lignifications and secondary wall formation. In compatible interactions (B301 – SG4z), multiple defense pathways were repressed, including those involved in lignin biosynthesis and secondary cell wall modifications, while cellular transport processes for nitrogen and sulfur were increased.ConclusionDistinct changes in global gene expression profiles occur in host roots following successful and unsuccessful attempted parasitism by Striga. Induction of specific defense related genes and pathways defines components of a unique resistance mechanism. Some genes and pathways up-regulated in the host resistance response to SG3 are repressed in the susceptible interactions, suggesting that the parasite is targeting specific components of the host’s defense. These results add to our understanding of plant-parasite interactions and the evolution of resistance to parasitic weeds.

SHR4z, a novel decoy effector from the haustorium of the parasitic weed Striga gesnerioides, suppresses host plant immunity

“…). Previous studies from our group (Huang et al , ; Mellor, ) have shown that RNAi silencing of the transcriptional activator VuGRF leads to a loss of the SG3‐induced HR. Similarly, silencing the expression of genes involved in cell wall modification (e.g.…”

The genetics underlying natural variation of plant–plant interactions, a beloved but forgotten member of the family of biotic interactions

“…For example, the expression of WRKY45 , a regulator of the salicylic acid/benzothiadiazole pathway, was highly induced in Striga hermonthica ‐infected rice (Mutuku et al ., ). In a study on an incompatible interaction with Striga gesnerioides , an up‐regulation was observed in Vigna unguiculata for genes underlying programmed cell death and apoptosis (Huang et al ., ). In addition, the authors noticed that some genes and pathways up‐regulated in V .…”

“…This observation highlights the complementarity of identifying the genetic and molecular mechanisms underlying plant–plant interactions in artificial environments simulating plant–plant interactions and in environments where focal plants have been directly challenged by neighbor plants. We should also mention that: (i) very few candidate genes have been identified as being involved in nutrient competition (Masclaux et al ., ); (ii) the function of the up‐regulated and down‐regulated genes can be highly dependent on the genotype tested, as found in barley and maize (St. Pierre et al ., ; Choe et al ., ); and (iii) several studies reported a substantial fraction of genes with unknown functions in their list of candidate genes (Horvath et al ., ; Broz et al ., ; Swarbrick et al ., ; Dita et al ., ; Biedrzycki et al ., ; Huang et al ., ; Schmid et al ., ; Baron et al ., ). The latter result suggests that some molecular mechanisms of neighbor perception and signaling pathways involved in the trigger of a response strategy remain to be identified.…”

Physico-chemical and functional properties of cowpea protein isolate as affected by the dehydration technique

“…Cowpeas (Vigna unguiculata) have an annual global production of 12.5 million tons (Huang et al, 2012), grow well in a diverse range of conditions and environments and contain only moderate levels of bioactive/anti-nutritional factors. It has potential of becoming an industrial crop.…”