Orman-Ligeza, Beata and Morris, Emily C. and Parizot, Boris and Livigne, Tristan and Babe, Aurelie and Ligeza, Aleksander and Klein, Stephanie and Sturrock, Craig D. and Xuan, Wei and Novák, Ondřey and Ljung, Karin and Fernandez, Maria and Rodriguez, Pedro L. and Dodd, Ian Charles and De Smit, Ive and Chaumont, Francois and Batoko, Henri and Périlleux, Claire and Lynch, Jonathan P. and Bennett, Malcolm J. and Beeckman, Tom and Draye, Xavier (2018) The xerobranching response represses lateral root formation when roots are not in contact with water. Current Biology, 28 (19). pp. 3165-3173. ISSN 0960-9822
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Abstract
Efficient soil exploration by roots represents an important target for crop improvement and food security [1, 2]. Lateral root (LR) formation is a key trait for optimising soil foraging for crucial resources such as water and nutrients. Here, we report an adaptive response termed xerobranching, exhibited by cereal roots, that represses branching when root tips are not in contact with wet soil. Non-invasive X-ray microCT imaging revealed that cereal roots rapidly repress LR formation as they enter an air space within a soil profile and are no longer in contact with water. Transcript profiling of cereal root tips revealed that transient water deficit triggers the abscisic acid (ABA) response pathway. In agreement with this, exogenous ABA treatment can mimic repression of LR formation under transient water deficit. Genetic analysis in Arabidopsis revealed that ABA repression of LR formation requires the PYR/PYL/RCARdependent signalling pathway. Our findings suggest that ABA acts as the key signal regulating xerobranching. We conclude that this new ABA-dependent adaptive mechanism allows roots to rapidly respond to changes in water availability in their local micro-environment and to use internal resources efficiently.