What is it about?

Gravitropism is the plant growth response to its position in relation to the gravity vector. It allows plants to optimise the use of limited and non-homogenous resources in their immediate environment. Historically, there have been three theories that have attempted to describe gravitropism: the starch-statolith theory for sensing, the Cholodny-Went model for signal transduction and growth control, and angle dependence for the behavior. While there has been hints that the three theories are connected, current literature does not fully capture root gravitropism in a way that integrates all its parts. In this work, we sought to reevaluate all the main components of the root graviresponse through the lens of angle-dependence. We found that all the components of the graviresponse, from sensing to response, were linked by angle dependence. Thanks to this approach, we were able to suggest new hypotheses regarding the different molecules that mediate the graviresponse via auxin transport and the existence of time-dependent features of root graviresponse.

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Why is it important?

Root architecture is a fundamental aspect of plant productivity, particularly in environments characterized by low or heterogeneous nutrient and water availability. Plants are able to adapt the spatial distribution of roots in the soil matrix, i.e., root architecture, to optimize resource capture. The main determinant of root architecture are the non-vertical growing lateral roots. These non-vertical growth angles are genetically determined and maintained in relation to the gravity field, indicating that plants are able to discern between different angles. Therefore, if we want to manipulate root architecture, we first must understand angle dependence. Since agriculture is already limited by the availability of water and nutrients in many areas of the world, the ability to manipulate root architecture is fundamental to increase yield and deal with a changing climate.

Perspectives

This paper uses a simple yet powerful experimental design to make a connection that was not obvious before. Moreover, by generating a true framework, we were able to look at the data through its lens and make new hypotheses, that hopefully we will be able to test in the future.

Marta Del Bianco
Italian Space Agency

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This page is a summary of: Angle dependence as a unifying feature of root graviresponse modules, Proceedings of the National Academy of Sciences, November 2025, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2506400122.
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