To sense ambient light conditions in order to optimize their growth and development, plants employ a battery of photoreceptors responsive to light quality and quantity. Essential for the sensing of red and far-red (FR) light is the phytochrome family of photoreceptors. Among them, phytochrome A is special because it mediates responses to different light conditions, including both very low fluen...

Higher plants monitor their ambient light signals through red/far-red absorbing phytochromes and blue/UV-A light absorbing cryptochromes. Subsequent signaling cascades alter gene expression and initiate morphogenic responses. We previously isolated SHORT HYPOCOTYL UNDER BLUE1 (SHB1), a putative transcriptional coactivator in light signaling. SHB1 is homologous to the SYG1 protein family and con...

PIF3 is a phytochrome-interacting basic helix-loop-helix transcription factor that negatively regulates light responses, including hypocotyl elongation, cotyledon opening, and hypocotyl negative gravitropism. However, the role of PIF3 in chlorophyll biosynthesis has not been clearly defined. Here, we show that PIF3 also negatively regulates chlorophyll biosynthesis by repressing biosynthetic ge...

Excising plant tissues has been found to increase the activity of phenylalanine ammonia-lyase (EC 4.1.3.5) (1, 4, 11, 12). This increase is probably due to de novo synthesis of this enzyme, since inhibitors of protein synthesis block the rise of PAL' activity (4, 11, 12). We suggested earlier (4) that the increase of PAL in gherkin hypocotyl segments was due to the release into the medium of re...

The phytochrome family of red (R) and far-red (FR) light receptors (phyA-phyE in Arabidopsis) play important roles throughout plant development and regulate elongation growth during de-etiolation and under light. Phytochromes regulate growth through interaction with the phytohormones gibberellin, auxin, and brassinosteroid. Recently it has been established that jasmonic acid (JA), a phytohormon...

Recent reports suggest that NF-Y transcription factors are positive regulators of skotomorphogenesis in Arabidopsis thaliana. Three NF-YC genes (NF-YC3, NF-YC4, and NF-YC9) are known to have overlapping functions in photoperiod dependent flowering and previous studies demonstrated that they interact with basic leucine zipper (bZIP) transcription factors. This included ELONGATED HYPOCOTYL 5 (HY5...

Protein dephosphorylation by the serine/threonine protein phosphatase 2A (PP2A) modulates a broad array of cellular functions. PP2A normally acts as a heterotrimeric holoenzyme complex comprising a catalytic subunit bound by regulatory A and B subunits. Characterization of the regulatory A subunit isoforms (ROOTS CURL IN NAPHTHYLPHTHALAMIC ACID1 [RCN1], PP2AA2, and PP2AA3) of Arabidopsis thalia...

Anion channels are thought to participate in signal transduction and turgor regulation in higher plant cells. The regulation of hypocotyl cell elongation is a situation in which these channels could play important roles because it involves ionic fluxes that are implicated in turgor control and orchestrated by various signals. We have used a pharmacological approach to reveal the contribution of...

The Arabidopsis thaliana hypocotyl is widely used to study the effects of light and plant growth factors on cell elongation. To provide a framework for the molecular-genetic analysis of cell elongation in this organ, here we describe, at the cellular level, its morphology and growth and identify a number of characteristic, developmental differences between light-grown and dark-grown hypocotyls....

CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a well-known E3 ubiquitin ligase, functions as a central regulator of plant growth and photomorphogenic development in plants, including hypocotyl elongation. It has been well-established that, in darkness, COP1 targets many photomorphogenesis-promoting factors for ubiquitination and degradation in the nucleus. However, increasing evidence has shown that ...