Role of β-Oxidation in Jasmonate Biosynthesis and Systemic Wound Signaling in Tomato

Arabidopsis thalianaglutamate receptor-like (GLR) channels are amino acid-gated ion channels involved in physiological processes including wound signaling, stomatal regulation, and pollen tube growth. Here, fluorescence microscopy and genetics were used to confirm the central role of GLR3.3 in the amino acid-elicited cytosolic Ca2+increase inArabidopsisseedling roots. To elucidate the binding properties of the receptor, we biochemically reconstituted the GLR3.3 ligand-binding domain (LBD) and analyzed its selectivity profile; our binding experiments revealed the LBD preference forl-Glu but also for sulfur-containing amino acids. Furthermore, we solved the crystal structures of the GLR3.3 LBD in complex with 4 different amino acid ligands, providing a rationale for how the LBD binding site evolved to accommodate diverse amino acids, thus laying the grounds for rational mutagenesis. Last, we inspected the structures of LBDs from nonplant species and generated homology models for other GLR isoforms. Our results establish that GLR3.3 is a receptor endowed with a unique amino acid ligand profile and provide a structural framework for engineering this and other GLR isoforms to investigate their physiology.

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Two glutamate- and pH-regulated Ca2+ channels are required for systemic wound signaling in Arabidopsis

Science Signaling ◽

10.1126/scisignal.aba1453 ◽

2020 ◽

Vol 13 (640) ◽

pp. eaba1453 ◽

Cited By ~ 8

Author(s):

Qiaolin Shao ◽

Qifei Gao ◽

Dhondup Lhamo ◽

Hongsheng Zhang ◽

Sheng Luan

Keyword(s):

Long Distance ◽

Permeable Channel ◽

Constitutive Activation ◽

Whole Plant ◽

Wound Signaling ◽

Systemic Wound Signaling ◽

P Type ◽

Systemic Responses ◽

Ca2 Channels ◽

Systemic Signals

Plants defend against herbivores and nematodes by rapidly sending signals from the wounded sites to the whole plant. We investigated how plants generate and transduce these rapidly moving, long-distance signals referred to as systemic wound signals. We developed a system for measuring systemic responses to root wounding in Arabidopsis thaliana. We found that root wounding or the application of glutamate to wounded roots was sufficient to trigger root-to-shoot Ca2+ waves and slow wave potentials (SWPs). Both of these systemic signals were inhibited by either disruption of both GLR3.3 and GLR3.6, which encode glutamate receptor–like proteins (GLRs), or constitutive activation of the P-type H+-ATPase AHA1. We further showed that GLR3.3 and GLR3.6 displayed Ca2+-permeable channel activities gated by both glutamate and extracellular pH. Together, these results support the hypothesis that wounding inhibits P-type H+-ATPase activity, leading to apoplastic alkalization. This, together with glutamate released from damaged phloem, activates GLRs, resulting in depolarization of membranes in the form of SWPs and the generation of cytosolic Ca2+ increases to propagate systemic wound signaling.

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