Light-Sensing in Roots

Abstract

Light gradients in the soil have largely been overlooked in understanding plant responses to the environment. However, roots contain photoreceptors that may receive ambient light through the soil or piped light through the vascular cylinder. In recent experiments we demonstrated linkages between phototropin-1 photoreceptor production, root growth efficiency, and drought tolerance, suggesting that root plasticity in response to light signals contributes to the ecological niche of A. thaliana. However, the availability of light cues in natural soil environments is poorly understood, raising questions about the relevance of light-mediated root growth for fitness in nature. Additionally, photoreceptor expression is characterized by pleiotropy so unique functions cannot be clearly ascribed to root vs. shoot sensory mechanisms. These considerations show that challenges exist for resolving the contribution of light-sensing by roots to plant adaptation. We suggest that blue-light sensing in roots of A. thaliana provides a model system for addressing these challenges. By calibrating blue light gradients in soils of diverse A. thaliana habitats and comparing fitness of phot1 mutant and wild-type controls when grown in presence or absence of soil light cues, it should be possible to elucidate the ecological significance of light-mediated plasticity in roots.

Physiological characterization and genetic modifiers of aberrant root thigmomorphogenesis in mutants of Arabidopsis thaliana MILDEW LOCUS O genes

“…Although roots are underground organs, they are able to perceive light penetrating into the soil (Galen et al . 2007a,b; Kutschera & Briggs ). Light perception by roots is important for many developmental aspects as well as for positive gravitropism (Feldman & Gildow ) or drought tolerance (Galen et al .…”

Understanding phototropism: from Darwin to today

“…Three life history traits in particular were shown to be influenced dramatically by the ability of a root to access water in arid conditions: (i) seedling establishment, (ii) accumulation of biomass in established plants, and (iii) fecundity of plants reaching adulthood (Galen et al, 2007a). These studies provide an exciting potential avenue to develop plants capable of growing in more arid environment that maintain, or even increase, their production value through genetic engineering of phot1 signalling (Galen et al, 2007b).…”

The blue light receptor Phototropin 1 suppresses lateral root growth by controlling cell elongation

“…Root negative phototropism can be regulated by weak light signals in the soil (Galen et al . , ,b). Root negative phototropism may serve to optimise the orientation of the root system, especially near the soil surface through which a variable amount of light might penetrate depending on soil type (Mandoli et al .…”