SUPPRESSOR OF MORE AXILLARY GROWTH2 1 Controls Seed Germination and Seedling Development in Arabidopsis
Open Access
- 26 July 2013
- journal article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 163 (1), 318-330
- https://doi.org/10.1104/pp.113.221259
Abstract
Abiotic chemical signals discovered in smoke that are known as karrikins (KARs) and the endogenous hormone strigolactone (SL) control plant growth through a shared MORE AXILLARY GROWTH2 (MAX2)-dependent pathway. A SL biosynthetic pathway and candidate KAR/SL receptors have been characterized, but signaling downstream of MAX2 is poorly defined. A screen for genetic suppressors of the enhanced seed dormancy phenotype of max2 in Arabidopsis (Arabidopsis thaliana) led to identification of a suppressor of max2 1 (smax1) mutant. smax1 restores the seed germination and seedling photomorphogenesis phenotypes of max2 but does not affect the lateral root formation, axillary shoot growth, or senescence phenotypes of max2. Expression of three transcriptional markers of KAR/SL signaling, D14-LIKE2, KAR-UP F-BOX1, and INDOLE-3-ACETIC ACID INDUCIBLE1, is rescued in smax1 max2 seedlings. SMAX1 is a member of an eight-gene family in Arabidopsis that has weak similarity to HEAT SHOCK PROTEIN 101, which encodes a caseinolytic peptidase B chaperonin required for thermotolerance. SMAX1 and the SMAX1-like (SMXL) homologs are differentially expressed in Arabidopsis tissues. SMAX1 transcripts are most abundant in dry seed, consistent with its function in seed germination control. Several SMXL genes are up-regulated in seedlings treated with the synthetic SL GR24. SMAX1 and SMXL2 transcripts are reduced in max2 seedlings, which could indicate negative feedback regulation by KAR/SL signaling. smax1 seed and seedling growth mimics the wild type treated with KAR/SL, but smax1 seedlings are still responsive to 2H-furo[2,3-c]pyran-2-one (KAR2) or GR24. We conclude that SMAX1 is an important component of KAR/SL signaling during seed germination and seedling growth but is not necessary for all MAX2-dependent responses. We hypothesize that one or more SMXL proteins may also act downstream of MAX2 to control the diverse developmental responses to KARs and SLs.Keywords
This publication has 65 references indexed in Scilit:
- Smoke-derived karrikin perception by the α/β-hydrolase KAI2 from ArabidopsisProceedings of the National Academy of Sciences of the United States of America, 2013
- Crystal structures of two phytohormone signal-transducing α/β hydrolases: karrikin-signaling KAI2 and strigolactone-signaling DWARF14Cell Research, 2013
- Strigolactone signaling is required for auxin-dependent stimulation of secondary growth in plantsProceedings of the National Academy of Sciences of the United States of America, 2011
- F-box protein MAX2 has dual roles in karrikin and strigolactone signaling in Arabidopsis thalianaProceedings of the National Academy of Sciences of the United States of America, 2011
- Strigolactones as Germination Stimulants for Root Parasitic PlantsPlant and Cell Physiology, 2010
- New Algorithms and Methods to Estimate Maximum-Likelihood Phylogenies: Assessing the Performance of PhyML 3.0Systematic Biology, 2010
- Karrikins enhance light responses during germination and seedling development in Arabidopsis thalianaProceedings of the National Academy of Sciences of the United States of America, 2010
- Loss of function of four DELLA genes leads to light- and gibberellin-independent seed germination in ArabidopsisPlanta, 2005
- A gene expression map of Arabidopsis thaliana developmentNature Genetics, 2005
- A new mathematical model for relative quantification in real-time RT-PCRNucleic Acids Research, 2001