Studying gravitropism in lateral roots

Arabidopsis seedlings showing lateral rootsQuick, what’s the first thing you think of when you think about plants? A tree? Leaves? A flower? Chances are slim that you thought first of a root, yet roots make up nearly half of the typical plant’s body. They are the hidden side of the plant, feeling their way in the dark, around stones and through soil, in search of the water and minerals needed for survival. They sense things like moisture gradients, solid objects like rocks and pebbles, and can tell up from down, using these cues in ways that remain largely unknown to guide their growth. Considering that we humans are completely dependent upon our photosynthetic, green cousins for the food we eat and the air we breathe, and considering the vulnerability of plants to drought, we would do well to learn more about how roots do what they do.

Despite making up the vast majority of the root system, how lateral roots choose their path remains uncharted territory. For example, lateral roots are content to grow sideways for long periods, a situation that is anathema to primary roots, which react swiftly with a course correction when they find themselves growing sideways. It isn’t like lateral roots are unable, however, to mount such a course correction. When displaced from their route, they will return to it, whatever it was. But when the course was not-quite-vertical, how do they know where to go? Are they using the same cellular tools as the primary root to detect gravity? Are the same circuits that activate curvature in the primary root activated in lateral roots? Given their role in nutrient uptake, do lateral roots change their course when nutrient conditions change? In our most recent paper, we set out to address some of these questions about lateral root growth. Over the coming weeks, I’ll be posting more on how we carried out our experiments and what we found out.

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