The new trend in cancer research is to view a tumor’s malignancy not as solely determined by the tumor’s damaged genome. That view may be somewhat intuitive and has been dominant for decades, but there’s evidence that a cancer’s behavior is determined by the interplay between the tumor itself (the seed) and the environment in which it resides (the soil). Doctors have long observed that the “same” tumor acts differently in different people and in different organs within the same person; this new paradigm could begin to explain why.

A key part of that environment are its microorganisms. Recent results show that microbes associated with tumors can metabolize the chemotherapy meant to treat the cancer. And this week, we’re learning that microbes also influence the original seed-and-soil—the non-metaphorical one involving actual plants.



It’s not only a plant’s genetic makeup that dictates whether it will thrive in a given environment; that environment, and the way each plant interacts with it, is critical. This idea was reinforced through a study that used pinyon pines, combining controlled experiments in a greenhouse and garden with observational studies of trees in the wild, made over 20 years (the latter 10 of which included a drought). Results from the different venues corroborated each other.

Pinyon pines, like other trees, need fungal partners. Trees can only draw in nutrients from the tips of their roots, and that is not nearly enough to support them. Fungi provide the trees with nutrients and minerals; in exchange, the trees feed the fungi some sugar so the fungi can grow.

These pinyon trees are a great model system for this type of study for a number of reasons. They are the only species in their habitat colonized by a specific type of fungus, allowing researchers to isolate the fungi’s effects. There are well defined drought-tolerant and drought-intolerant trees, a property that’s genetically determined. The two are easily distinguishable in the field, since the ones that are drought-tolerant happen to be moth-susceptible. In non-drought conditions, they get preferentially eaten by moths and, therefore, look different.

Researchers took seeds from drought-tolerant and drought-intolerant trees, then exposed them to soil containing fungal communities from both drought-tolerant and drought-intolerant roots. Even when grown with the opposite soil, the seeds ignored the local fungal community; both drought-tolerant and drought-intolerant seeds still cultivated the same species of fungus as their adult forbears.

It turned out that the inheritance of the fungus is what actually made the different trees drought-tolerant or drought intolerant; seeds from drought-tolerant mothers only grew larger than their drought-intolerant cousins when in the presence of their attendant fungi. The tree’s genetics simply helped it recruit specific species of fungi.

A 15-month-long drought in 2002-2003 killed more than 90 percent of pinyon trees in the Southwestern US, and further droughts are a projected consequence of our warming planet. Understanding these types of interactions between a plant’s genetics and its environmental—and the impacts these interactions can have on plant survival under varying conditions—is going to be invaluable if we are interested in effective forest management and restoration as our climate becomes more and more erratic. And similar things might be going on with plants we use commercially, like crops.

PNAS, 2017. DOI: 10.1073/pnas.1704022114 (About DOIs).