A chemical genetics approach reveals a role of brassinolide and cellulose synthase in hypocotyl elongation of etiolated Arabidopsis seedlings

Abstract

The development of juvenile seedlings after germination is critical for the initial establishment of reproductive plants. Ethylene plays a pivotal role in the growth of seedlings under light or dark during early development. Previously, we identified small molecules sharing a quinazolinone backbone that suppressed the constitutive triple response phenotype in dark-grown eto1-4 seedlings. We designated these small molecules as ACSinhibitor quinazolinones (acsinones), which were uncompetitive inhibitors of 1-aminocyclopropane-1-carboxylic acid synthase. To explore the additional roles of acsinones in plants, we screened and identified 19 Arabidopsis mutants with reduced sensitivity to acsinone7303, which were collectively named revert to eto1 (ret) because of their recovery of the eto1 phenotype. A map-based cloning approach revealed that CELLULOSE SYNTHASE6 (CESA6) and DE-ETIOLATED2 (DET2) were mutated in ret8 (cesa6(ret8);eto1-4) and ret41 (det2(ret41);eto1-5), respectively. Etiolated seedlings of both ret8 and ret41 exhibit short hypocotyls and roots. Ethylene levels were similar in etiolated cesa6(ret8) and det2-1 and in eto1 mutants treated with acsinone7303. Chemical inhibitors of ethylene biosynthesis and perception did not significantly suppress the etiolated phenotype of cesa6(ret8) and det2(ret41). However, together with eto1, cesa6(ret8) and det2(ret41) exhibited an enhanced phenotype in the hypocotyls and apical hooks of etiolated seedlings. These results confirm that, in addition to ethylene, cellulose synthesis and brassinolides can independently contribute to modulate hypocotyl development in young seedlings.

Karrikins: Regulators Involved in Phytohormone Signaling Networks during Seed Germination and Seedling Development

“…Numerous studies showed that IAA, GA and brassinolide induce the elongation of hypocotyl by promoting cell elongation (Lilley et al, 2012; Chen et al, 2013; Bernardo-García et al, 2014; Oh et al, 2014). Further, both GA and brassinolide regulate hypocotyl growth in an IAA-dependent manner (Stamm and Kumar, 2010; Chapman et al, 2012; Zhou X.-Y.…”

Crosstalk between Brassinosteroids and Ethylene during Plant Growth and under Abiotic Stress Conditions

“…Another study dealing with the influence of ethylene and BRs on hypocotyl development was published in 2013 [ 13 ]. The study involved screening and identifying mutant plants of Arabidopsis with an altered response to acsinone7303, which is a small molecule that can act like an uncompetitive inhibitor of ACS.…”

“…However, an abundance of ethylene in eto1 enhanced the short hypocotyl phenotype in cesa6 and det2 . Additional experiments with EBL treatment of eto1 , det2-1 , and det2 ret41 showed that the balance between levels of ethylene and BRs was important for proper regulation of hypocotyl growth [ 13 ].…”

Plant Chemical Genetics: From Phenotype-Based Screens to Synthetic Biology

“…In another screen, hypostatin resistance led to the identification of the glycoactivating enzymes but not to the direct target of the glycosylated hypostatin (Zhao et al, 2007). A screen for resistance to the ethylene biosynthesis inhibitor acsinone7303 detected 19 Arabidopsis mutants, designated revert to eto1, of which two carried mutations in the CELLULOSE SYNTHASE6 (CESA6) and DET2 genes, but none were direct targets (Chen et al, 2013). Similarly, in addition to mutations in CESA1 and CESA3, a forward genetic screen found two independent defective genes that encode pentatricopeptide repeat-like proteins and confer tolerance to C17 (Hu et al, 2016).…”