Plant hormones are the central regulators of plant growth and development. Eventhough, auxin, ethylene, ABA, cytokinin, gibberellin, brassinosteroid and jasmonic acid are considered to be the major plant hormones, still the significance of yet-uncharacterised growth substances like cinnamic acid (CA) on plants can not be underplayed. Cinnamic acid or phenylpropanoic acid is the precursor for the whole phenylpropanoid pathway. Cinnamic acid exists in two isoforms namely cis and trans. trans-CA is known as auxin like, inactive compound while cis-CA is known to play an array of plant growth and developmental aspects. In an effort to identify the genetic components involved in cis-CA mediated hypocotyl inhibition response, a genetic screen was initiated using Arabidopsis as a model plant. S...[ Read more ]

Plant hormones are the central regulators of plant growth and development. Eventhough, auxin, ethylene, ABA, cytokinin, gibberellin, brassinosteroid and jasmonic acid are considered to be the major plant hormones, still the significance of yet-uncharacterised growth substances like cinnamic acid (CA) on plants can not be underplayed. Cinnamic acid or phenylpropanoic acid is the precursor for the whole phenylpropanoid pathway. Cinnamic acid exists in two isoforms namely cis and trans. trans-CA is known as auxin like, inactive compound while cis-CA is known to play an array of plant growth and developmental aspects. In an effort to identify the genetic components involved in cis-CA mediated hypocotyl inhibition response, a genetic screen was initiated using Arabidopsis as a model plant. Screening of T-DNA insertion mutagenised lines for seedlings defective in hypocotyl inhibition yielded a mutant line christened as "cis-phenylpropanoic acid resistant" (cpar) and the subsequent genetic analysis showed that cpar is a recessive mutation and inherited as a single locus. Light grown cpar seedlings exhibit long yellow green hypocotyl. Global gene expression analysis using Affymetrix Arabidopsis whole genome array identified several target genes of cis-CA. Among the induced genes, GH3-4 (At1g59500) is highly induced by cis-CA confirmed by RNA gel blot analysis. Future study of cis-CA regulated gene expression using the GH3-4 gene will further advance our knowledge on the function of cis-CA in plant growth and development.