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F-box protein MAX2 has dual roles in karrikin and strigolactone signaling in Arabidopsis thaliana.

ABSTRACT: Smoke is an important abiotic cue for plant regeneration in postfire landscapes. Karrikins are a class of compounds discovered in smoke that promote seed germination and influence early development of many plants by an unknown mechanism. A genetic screen for karrikin-insensitive mutants in Arabidopsis thaliana revealed that karrikin signaling requires the F-box protein MAX2, which also mediates responses to the structurally-related strigolactone family of phytohormones. Karrikins and the synthetic strigolactone GR24 trigger similar effects on seed germination, seedling photomorphogenesis, and expression of a small set of genes during these developmental stages. Karrikins also repress MAX4 and IAA1 transcripts, which show negative feedback regulation by strigolactone. We demonstrate that all of these common responses are abolished in max2 mutants. Unlike strigolactones, however, karrikins do not inhibit shoot branching in Arabidopsis or pea, indicating that plants can distinguish between these signals. These results suggest that a MAX2-dependent signal transduction mechanism was adapted to mediate responses to two chemical cues with distinct roles in plant ecology and development.

SUBMITTER: Nelson DC

PROVIDER: S-EPMC3102411 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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F-box protein MAX2 has dual roles in karrikin and strigolactone signaling in Arabidopsis thaliana.

Nelson David C DC Scaffidi Adrian A Dun Elizabeth A EA Waters Mark T MT Flematti Gavin R GR Dixon Kingsley W KW Beveridge Christine A CA Ghisalberti Emilio L EL Smith Steven M SM

Proceedings of the National Academy of Sciences of the United States of America 20110509 21

Smoke is an important abiotic cue for plant regeneration in postfire landscapes. Karrikins are a class of compounds discovered in smoke that promote seed germination and influence early development of many plants by an unknown mechanism. A genetic screen for karrikin-insensitive mutants in Arabidopsis thaliana revealed that karrikin signaling requires the F-box protein MAX2, which also mediates responses to the structurally-related strigolactone family of phytohormones. Karrikins and the synthet ...[more]

PMID: 21555559

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Project description:The F-box protein MORE AXILLARY GROWTH 2 (MAX2) is a central component in the signaling cascade of strigolactones (SLs) as well as of the smoke-derived karrikins (KARs) and the so far unknown endogenous KAI2 ligand (KL). The two groups of molecules are involved in overlapping and unique developmental processes, and signal-specific outcomes are attributed to perception by the paralogous α/β-hydrolases DWARF14 (D14) for SL and KARRIKIN INSENSITIVE 2/HYPOSENSITIVE TO LIGHT (KAI2/HTL) for KAR/KL. In addition, depending on which receptor is activated, specific members of the SUPPRESSOR OF MAX2 1 (SMAX1)-LIKE (SMXL) family control KAR/KL and SL responses. As proteins that function in the same signal transduction pathway often occur in large protein complexes, we aimed at discovering new players of the MAX2, D14, and KAI2 protein network by tandem affinity purification in Arabidopsis cell cultures. When using MAX2 as a bait, various proteins were copurified, among which were general components of the Skp1-Cullin-F-box complex and members of the CONSTITUTIVE PHOTOMORPHOGENIC 9 signalosome. Here, we report the identification of a novel interactor of MAX2, a type 5 serine/threonine protein phosphatase, designated PHYTOCHROME-ASSOCIATED PROTEIN PHOSPHATASE 5 (PAPP5). Quantitative affinity purification pointed at PAPP5 as being more present in KAI2 rather than in D14 protein complexes. In agreement, mutant analysis suggests that PAPP5 modulates KAR/KL-dependent seed germination under suboptimal conditions and seedling development. In addition, a phosphopeptide enrichment experiment revealed that PAPP5 might dephosphorylate MAX2 in vivo independently of the synthetic SL analog, rac-GR24. Together, by analyzing the protein complexes to which MAX2, D14, and KAI2 belong, we revealed a new MAX2 interactor, PAPP5, that might act through dephosphorylation of MAX2 to control mainly KAR/KL-related phenotypes and, hence, provide another link with the light pathway.

Dataset Information

F-box protein MAX2 has dual roles in karrikin and strigolactone signaling in Arabidopsis thaliana.

Publications

F-box protein MAX2 has dual roles in karrikin and strigolactone signaling in Arabidopsis thaliana.

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