'happy on norflurazon' (hon) mutations implicate perturbance of plastid homeostasis with activating stress acclimatization and changing nuclear gene expression in norflurazon-treated seedlings

• P>Various mutant screens have been undertaken to identify constituents involved in the transmission of signals from the plastid to the nucleus. Many of these screens have been performed using carotenoid-deficient plants grown in the presence of norflurazon (NF), an inhibitor of phytoene desaturase. NF-treated plants are bleached and suppress the expression of nuclear genes encoding chloroplast proteins. Several genomes uncoupled (gun) mutants have been isolated that de-repress the expression of these nuclear genes. In the present study, a genetic screen has been established that circumvents severe photo-oxidative stress in NF-treated plants. Under these modified screening conditions, happy on norflurazon (hon) mutants have been identified that, like gun mutants, de-repress expression of the Lhcb gene, encoding a light-harvesting chlorophyll protein, but, in contrast to wild-type and gun mutants, are green in the presence of NF. hon mutations disturb plastid protein homeostasis, thereby activating plastid signaling and inducing stress acclimatization. Rather than defining constituents of a retrograde signaling pathway specifically associated with the NF-induced suppression of nuclear gene expression, as proposed for gun, hon mutations affect Lhcb expression more indirectly prior to initiation of plastid signaling in NF-treated seedlings. They pre-condition seedlings by inducing stress acclimatization, thereby attenuating the impact of a subsequent NF treatment.

Ämnesord

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Nyckelord

retrograde signaling

plastid homeostasis

norflurazon

hon mutants

Arabidopsis

chloroplast

MG-PROTOPORPHYRIN IX

DEPENDENT CLP PROTEASE

ARABIDOPSIS-THALIANA

SINGLET OXYGEN

SIGNALING PATHWAYS

TETRAPYRROLE BIOSYNTHESIS

CHLOROPLAST DEVELOPMENT

LEAF VARIEGATION

MOLECULAR-BASIS

MUTANT

REVEALS

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