Zoospore chemotaxis of closely related legume‐root infecting Phytophthora species towards host isoflavones

Abstract

Phytophthora niederhauserii, P. pisi, P. sojae and P. vignae are closely related species that are pathogenic to various legume plants. While P. sojae and P. vignae are reported to specifically infect soybean and cowpea, respectively, P. pisi is reported to attack pea and faba bean. Phytophthora niederhauserii is considered to have a broad host range. Zoospores of some Phytophthora species are chemotactically attracted to the isoflavones that are secreted by their host plants. The focus of the current study was to determine the chemotaxic behaviour of zoospores from closely related legume-root infecting Phytophthora species and to investigate the correlation, if any, to host preference as determined by greenhouse pathogenicity tests. The results showed that P. sojae and P. vignae were attracted to the non-soybean isoflavone prunetin as well as to the soybean isoflavones genistein and daidzein, which is in contrast with their host specificity on soybean and cowpea, respectively. On the other hand, P. pisi and P. niederhauserii were only attracted to prunetin, previously reported to be produced by pea, but not to the isoflavones associated with the non-host soybean. The lack of responsiveness to genistein and daidzein in P. pisi may represent a recent adaptation to the host specialization towards pea. However, the affinity of P. niederhauserii to prunetin shows that this trait can also be present in taxa not specifically associated with legume hosts.

Small molecules below‐ground: the role of specialized metabolites in the rhizosphere

“…sojae and P . vignae , have evolved reception mechanisms to recognize the same chemical signals released by legume roots, which highlights an evolutionary change to hijack a beneficial plant–microbe symbiosis (Hosseini et al ., ).…”

“…prunetin, genistein, and daidzein) (Figure 1), which play an important role in Rhizobium-legume symbiosis as chemoattractants, inducers for nodulation genes, and regulators of phytoalexin resistance (Hassan and Mathesius, 2012). The chemotactic oomycete pathogens, Phytophthora niederhauserii, P. pisi, P. sojae and P. vignae, have evolved reception mechanisms to recognize the same chemical signals released by legume roots, which highlights an evolutionary change to hijack a beneficial plant-microbe symbiosis (Hosseini et al, 2014).…”

Exchanges at the Plant-Oomycete Interface That Influence Disease

“…Lysis of the host during infection by the necrotroph occurs due to the absence of defense-suppressing effectors, ROS generation, and early expression of NLPs, as discussed in Box 3. specifically to prunetin (Sekizaki et al, 1993), while Ph. sojae responds to daizein and genistein, which are produced by their respective hosts (Hosseini et al, 2014). These isoflavones also influence encystment and germ tube orientation (Morris et al, 1998).…”

Unclear Intentions: Eavesdropping in Microbial and Plant Systems

“…Pathogenic microbes can eavesdrop on host signals to coordinate infection. In plant roots, for example, oomycete parasites can more easily find their host by eavesdropping on signals involved in attracting rhizobial partners (Hosseini et al, 2014). Inside the human gut E. coli and Salmonella respond to adrenaline and noradrenaline activating genes involved in virulence and motility (Lyte, 1992;Clarke et al, 2006).…”