SUPPRESSOR OF MORE AXILLARY GROWTH2 1 Controls Seed Germination and Seedling Development in Arabidopsis

We report the identification and characterization of SUPPRESSOR OF MORE AXILLARY GROWTH2 1

John P. Stanga; Steven M. Smith; Winslow R. Briggs; David C. Nelson

2013

Scholarcy highlights

  • Strigolactones and karrikins comprise two classes of butenolide signaling molecules that stimulate seed germination
  • Abiotic chemical signals discovered in smoke that are known as karrikins and the endogenous hormone strigolactone control plant growth through a shared MORE AXILLARY GROWTH2-dependent pathway
  • SUPPRESSOR OF MAX2 1 and SMXL2 transcripts are reduced in max seedlings, which could indicate negative feedback regulation by KAR/SL signaling. smax seed and seedling growth mimics the wild type treated with KAR/SL, but smax seedlings are still responsive to 2H-furopyran-2-one or GR24
  • To identify genes that may act downstream of MAX2 in KAR/SL signaling pathways, we performed a genetic screen for smax mutants
  • The max mutant was previously isolated as a frameshift allele of MAX2 from a γ-ray mutagenized population of Landsberg erecta seeds
  • Hypocotyl elongation of smax max was reduced to approximately 66% of the length of max, at approximately 6 mm versus approximately 10 mm, respectively. smax max hypocotyls were significantly shorter than the wild-type grown on media lacking KAR/GR24 and were similar in length to wild-type seedlings treated with 1 μm KAR1 or KAR2
  • Recognizing that mutations in genes that are not specific to the MAX2 pathway could confound a screen based on germination alone, we filtered putative smax mutants by testing for suppression of multiple max phenotypes. smax was chosen for further study, mapped, and identified as a premature stop codon in the previously uncharacterized gene At5g57710
  • Cotyledonary petiole growth and IAA1 expression were not significantly affected in smax seedlings but were restored to wild-type phenotypes in smax max

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