stress tolerance of dodder could also be influenced by these host-derived mobile
substances that are capable of interspecies trafficking.
The holostemparasitic plant Cuscuta can serve as an important system for studies
on plant-plant interactions. Different responses from host plants to Cuscuta might be
able to partially clarify some potential tendencies of plant stress response between
different plant taxa and may also suggest unknown stress response mechanisms in
host plants. Furuhashi et al. [73] used a unique experimental system to analyze
Cuscuta japonica seedlings under FR light and/or with a contact signal attached to
different host plants. Cuscuta attached to Pueraria thunbergiana showed a higher
(>20%) mol percentage of pinitol both in the apical and middle regions (haustorium
part). Cuscuta japonica attached to Buxus microphylla and Conyza sumatrensis
contained less pinitol, and values were even lower than in C. japonica seedlings
before parasitization. Although C. japonica attached to Pueraria did not contain
large amounts of glucose and sucrose, C. japonica attached to Buxus and Conyza did
especially in the haustorium-induced parts. Host plants without C. japonica parasitization clearly showed different metabolite profilings from C. japonica seedlings.
Pinitol was dominant in Pueraria, and quinic acid was dominant in Conyza and
Buxus. Also, glucose, myoinositol, and oxalic acid were bigger in both Conyza and
Buxus, but not in Pueraria.
Parasite plants are clearly plants and have the same plant hormonal system and
physiological response. This implies that host plants would not always be able to use
the same defense strategy against parasite plants. This consideration gave rise to
discussions about comparing parasite plants with herbivores [74]. Although parasite
plants have been recognized as weeds that cause agricultural problems, triggering
some interest [75, 76], parasitization does not always negatively influence the host
plant. For example, tomatoes parasitized by Cuscuta altered certain plant hormones
(e.g., salicylic acid) and can influence their defense system against insect herbivores
[13]. Also, Runyon et al. [61] used a metabolomic profiling approach involving
vapor phase extraction to measure changes in phytohormones occurring within
tomato plants during parasitism by C. pentagona. Theirs results indicated that
parasite seedlings elicit a relative paucity of host reactions when first attaching to
10-day-old tomato seedlings, whereas a second attachment by the growing parasite
vine 10 days later induced large increases in several plant hormones and a strong
HLR (hypersensitive-like response). Also, Runyon et al. [61] assessed the effectiveness of SA (salicylic acid)- and JA (jasmonic acid)-mediated host changes using
transgenic and mutant plants. These methods give the first picture of the composition
and timing of hormonal signalling induced in response to a parasitic plant. They
conclude that as with herbivore and pathogen attack, plants are able to perceive
invasion by parasitic plant haustoria and respond by activating induced defense
pathways. Seedlings of C. pentagona elicited relatively few changes in the host upon
first attachment to young tomato seedlings, possibly because of ontogenetic constraints in host defense or because the parasite is better able to manipulate young
hosts. Older tomato plants responded to a second attachment by activating the JA
and SA signalling pathways, both of which appear to mediate defenses that effectively reduce parasite growth. Parasitism also induced increases in ABA (abscisic
5 Field Dodder: Life Cycle and Interaction with Host Plants
109
substances that are capable of interspecies trafficking.
The holostemparasitic plant Cuscuta can serve as an important system for studies
on plant-plant interactions. Different responses from host plants to Cuscuta might be
able to partially clarify some potential tendencies of plant stress response between
different plant taxa and may also suggest unknown stress response mechanisms in
host plants. Furuhashi et al. [73] used a unique experimental system to analyze
Cuscuta japonica seedlings under FR light and/or with a contact signal attached to
different host plants. Cuscuta attached to Pueraria thunbergiana showed a higher
(>20%) mol percentage of pinitol both in the apical and middle regions (haustorium
part). Cuscuta japonica attached to Buxus microphylla and Conyza sumatrensis
contained less pinitol, and values were even lower than in C. japonica seedlings
before parasitization. Although C. japonica attached to Pueraria did not contain
large amounts of glucose and sucrose, C. japonica attached to Buxus and Conyza did
especially in the haustorium-induced parts. Host plants without C. japonica parasitization clearly showed different metabolite profilings from C. japonica seedlings.
Pinitol was dominant in Pueraria, and quinic acid was dominant in Conyza and
Buxus. Also, glucose, myoinositol, and oxalic acid were bigger in both Conyza and
Buxus, but not in Pueraria.
Parasite plants are clearly plants and have the same plant hormonal system and
physiological response. This implies that host plants would not always be able to use
the same defense strategy against parasite plants. This consideration gave rise to
discussions about comparing parasite plants with herbivores [74]. Although parasite
plants have been recognized as weeds that cause agricultural problems, triggering
some interest [75, 76], parasitization does not always negatively influence the host
plant. For example, tomatoes parasitized by Cuscuta altered certain plant hormones
(e.g., salicylic acid) and can influence their defense system against insect herbivores
[13]. Also, Runyon et al. [61] used a metabolomic profiling approach involving
vapor phase extraction to measure changes in phytohormones occurring within
tomato plants during parasitism by C. pentagona. Theirs results indicated that
parasite seedlings elicit a relative paucity of host reactions when first attaching to
10-day-old tomato seedlings, whereas a second attachment by the growing parasite
vine 10 days later induced large increases in several plant hormones and a strong
HLR (hypersensitive-like response). Also, Runyon et al. [61] assessed the effectiveness of SA (salicylic acid)- and JA (jasmonic acid)-mediated host changes using
transgenic and mutant plants. These methods give the first picture of the composition
and timing of hormonal signalling induced in response to a parasitic plant. They
conclude that as with herbivore and pathogen attack, plants are able to perceive
invasion by parasitic plant haustoria and respond by activating induced defense
pathways. Seedlings of C. pentagona elicited relatively few changes in the host upon
first attachment to young tomato seedlings, possibly because of ontogenetic constraints in host defense or because the parasite is better able to manipulate young
hosts. Older tomato plants responded to a second attachment by activating the JA
and SA signalling pathways, both of which appear to mediate defenses that effectively reduce parasite growth. Parasitism also induced increases in ABA (abscisic
5 Field Dodder: Life Cycle and Interaction with Host Plants
109