Sphynolactone-7 is a potent stimulant — that induces parasitic plant germination, causing it to die

This topic might seem a little bit bizarre, or obtuse — as far as the gene-environment interactions theme of these GEITP pages. On the other hand, it might reflect my subconscious desire to have been a plant molecular biologist.

However, in my opinion, “the environment” here is the parasite and “the genes” are those in the roots of the host crop that respond to that environmental signal. Striga hermonthica (Striga) are parasitic weeds (e.g. broomrapes, witchweeds) that infect roots of crops such as sorghum, millet, maize, rapeseed, tomato, sunflower, and legumes. These obligate parasites (i.e. those dependent on a host for their survival) use their host to grow and on which to reproduce. Striga only germinate in the presence of a germination stimulant originating from the host root. So, here we even have a gene-environment interaction within a gene-environment interaction [i.e. genes of the parasite are responding to a germination signal (their environment) from the host; and genes of the host are responding to a signal (the environment) from the parasite].

1. There is an agricultural need to find some efficient means of protecting crops from the tiny Striga seeds buried in the soil. If infestation can be suppressed, millions of dollars in the food industry could be saved. A group of host-generated small-molecule hormones, called strigolactones (SLs), are known to induce germination of Striga seeds. If Striga germinates in the absence of the host, the germination process is lethal; this knowledge has convinced researchers to develop SL agonists (‘agonists’ are substances that initiate a physiological response when bound to a receptor; an agonist substitutes for the ‘normal’ signal and elicits an action, whereas an antagonist blocks an action). Such agonists could therefore act as inducers of suicidal germination — to purge the soil of viable Striga seeds.


Of course, development of any potent and accessible compounds must act only on Striga — without impeding normal crop development. Authors [see attached article & editorial] describe herein the development of a Striga-selective SL agonist that acts as a potent synthetic germination stimulant in the femtomolar range (having a concentration of 10-15 moles per liter). Thus, this might be the successful development of an agrochemical (sphynolactone-7) that may be used to germinate parasitic weeds in the absence of a host (so that they will die, called suicide germination) and hopefully to provide insight into what subcellular mechanism(s) determine(s) specificity of these parasites.


Science 14 Dec 2o18; 362: 1301–1305 [article] & pp 1248-1249 [editorial]

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