Photochemical Characterization of Phytochrome Missense Mutants

Shin, Ah-Young; Kim, Hwan-Sik; Lee, Si-Seok; Kim, Min-Gon; Han, Yun‐Jeong; Song, Pill‐Soon; Kim, Jeong-Il

doi:10.1271/bbb.110555

Cited by 1 publication

(2 citation statements)

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“…Previous studies have established that the G767R mutation inhibits light-dependent nuclear localization of phyB while not altering its chromophorylation, photochemistry, dark reversion or dimerization (Wagner and Quail 1995 ; Matsushita et al 2003 ; Shin et al 2011 ). This inability to migrate into the nucleus accounts for the loss of function of phyB G767R , since addition of an NLS restores the nuclear localization and photoregulatory activity of a GFP-fusion of this LOF allele (Matsushita et al 2003 ).…”

Section: Resultsmentioning

confidence: 99%

“…The G767R mutation has long been known to profoundly suppress phyB signaling function (Wagner and Quail 1995 ; Matsushita et al 2003 ). Since this mutation is located outside the N-terminal photosensory module (PSM) of the full-length photoreceptor, it does not alter the photochemical property of phyB in vivo or in vitro (Wagner and Quail 1995 ; Shin et al 2011 ). Instead, this mutation inhibits phyB nuclear import (Matsushita et al 2003 ; Pfeiffer et al 2012 ).…”

Section: Discussionmentioning

confidence: 99%

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A cytosol-tethered YHB variant of phytochrome B retains photomorphogenic signaling activity

Hu,

Lagarias

2024

Plant Mol Biol

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The red and far-red light photoreceptor phytochrome B (phyB) transmits light signals following cytosol-to-nuclear translocation to regulate transcriptional networks therein. This necessitates changes in protein–protein interactions of phyB in the cytosol, about which little is presently known. Via introduction of a nucleus-excluding G767R mutation into the dominant, constitutively active phyBY276H (YHB) allele, we explore the functional consequences of expressing a cytosol-localized YHBG767R variant in transgenic Arabidopsis seedlings. We show that YHBG767R elicits selective constitutive photomorphogenic phenotypes in dark-grown phyABCDE null mutants, wild type and other phy-deficient genotypes. These responses include light-independent apical hook opening, cotyledon unfolding, seed germination and agravitropic hypocotyl growth with minimal suppression of hypocotyl elongation. Such phenotypes correlate with reduced PIF3 levels, which implicates cytosolic targeting of PIF3 turnover or PIF3 translational inhibition by YHBG767R. However, as expected for a cytoplasm-tethered phyB, YHBG767R elicits reduced light-mediated signaling activity compared with similarly expressed wild-type phyB in phyABCDE mutant backgrounds. YHBG767R also interferes with wild-type phyB light signaling, presumably by formation of cytosol-retained and/or otherwise inactivated heterodimers. Our results suggest that cytosolic interactions with PIFs play an important role in phyB signaling even under physiological conditions.

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