Nuclear import and export of proteins in plants: a tool for the regulation of signalling

Merkle, Thomas

doi:10.1007/s004250100621

Cited by 59 publications

(44 citation statements)

References 146 publications

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“…The dual nuclear and cytoplasmic localization of ULT1 and ULT2 proteins is not unprecedented among the SAND domain-containing proteins (Halonen et al, 2004;Ramsey et al, 2002). One possibility is that the dual localization in the nucleus and the cytosol may serve as a modulation mechanism for transcriptional regulation, as shown for some families of transcription factors in plants and animals (Fabbro and Henderson, 2003;Merkle, 2001;Ziegelbauer et al, 2001). …”

Section: Discussionmentioning

confidence: 99%

ULTRAPETALA1encodes a SAND domain putative transcriptional regulator that controls shoot and floral meristem activity inArabidopsis

et al. 2005

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The higher-plant shoot apical meristem is a dynamic structure continuously producing cells that become incorporated into new leaves, stems and flowers. The maintenance of a constant flow of cells through the meristem depends on coordination of two antagonistic processes: self-renewal of the stem cell population and initiation of the lateral organs. This coordination is stringently controlled by gene networks that contain both positive and negative components. We have previously defined the ULTRAPETALA1(ULT1) gene as a key negative regulator of cell accumulation in Arabidopsis shoot and floral meristems, because mutations in ULT1 cause the enlargement of inflorescence and floral meristems, the production of supernumerary flowers and floral organs, and a delay in floral meristem termination. Here, we show that ULT1 negatively regulates the size of the WUSCHEL (WUS)-expressing organizing center in inflorescence meristems. We have cloned the ULT1 gene and find that it encodes a small protein containing a B-box-like motif and a SAND domain, a DNA-binding motif previously reported only in animal transcription factors. ULT1 and its Arabidopsis paralog ULT2 define a novel small gene family in plants. ULT1 and ULT2 are expressed coordinately in embryonic shoot apical meristems, in inflorescence and floral meristems, and in developing stamens, carpels and ovules. Additionally, ULT1 is expressed in vegetative meristems and leaf primordia. ULT2 protein can compensate for mutant ULT1 protein when overexpressed in an ult1 background, indicating that the two genes may regulate a common set of targets during plant development. Downregulation of both ULT genes can lead to shoot apical meristem arrest shortly after germination, revealing a requirement for ULT activity in early development.

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Section: Discussionmentioning

confidence: 99%

ULTRAPETALA1encodes a SAND domain putative transcriptional regulator that controls shoot and floral meristem activity inArabidopsis

et al. 2005

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“…The two most common NLSs are monopartite signals, which are short stretches enriched in basic amino acids, and bipartite signals, which are composed of two short basic stretches separated by a spacer (Merkle, 2001). The monopartite NLS depicted for WRKY proteins is conserved in SUSIBA2 (amino acids 328 to 331; Figure 2).…”

Section: Susiba2 Belongs To the Wrky Superfamily Of Transcription Facmentioning

confidence: 99%

A Novel WRKY Transcription Factor, SUSIBA2, Participates in Sugar Signaling in Barley by Binding to the Sugar-Responsive Elements of theiso1Promoter [W]

et al. 2003

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SURE (sugar responsive) is a cis element in plant sugar signaling. The SURE element was reported first for potato, in which it confers sugar responsiveness to the patatin promoter. A SURE binding transcription factor has not been isolated. We have isolated a transcription factor cDNA from barley and purified the corresponding protein. The transcription factor, SUSIBA2 (sugar signaling in barley), belongs to the WRKY proteins and was shown to bind to SURE and W-box elements but not to the SP8a element in the iso1 promoter. Nuclear localization of SUSIBA2 was demonstrated in a transient assay system with a SUSIBA2:green fluorescent protein fusion protein. Exploiting the novel transcription factor oligodeoxynucleotide decoy strategy with transformed barley endosperm provided experimental evidence for the importance of the SURE elements in iso1 transcription. Antibodies against SUSIBA2 were produced, and the expression pattern for susiba2 was determined at the RNA and protein levels. It was found that susiba2 is expressed in endosperm but not in leaves. Transcription of susiba2 is sugar inducible, and ectopic susiba2 expression was obtained in sugar-treated leaves. Likewise, binding to SURE elements was observed for nuclear extracts from sugar-treated but not from control barley leaves. The temporal expression of susiba2 in barley endosperm followed that of iso1 and endogenous sucrose levels, with a peak at ‫ف‬ 12 days after pollination. Our data indicate that SUSIBA2 binds to the SURE elements in the barley iso1 promoter as an activator. Furthermore, they show that SUSIBA2 is a regulatory transcription factor in starch synthesis and demonstrate the involvement of a WRKY protein in carbohydrate anabolism. Orthologs to SUSIBA2 were isolated from rice and wheat endosperm.

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“…The gradient of Ran-GTP across the nuclear envelope, because of asymmetric distribution of hydrolase and nucleotide exchange activities, is the key regulator of the directionality of nuclear transport across nuclear pore complexes. Nuclear transport has been less studied in plants than in mammals and yeast but basic mechanisms, including the importance of Ran-GTP gradient, appear to be conserved (45). Plant Ran proteins contain two additional conserved cysteines absent in nonphotosynthetic eukaryotes (Fig.…”

Section: Figmentioning

confidence: 99%

New thioredoxin targets in the unicellular photosynthetic eukaryote Chlamydomonas reinhardtii

Lemaire

Guillon

Maréchal

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

235

189

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Proteomics were used to identify the proteins from the eukaryotic unicellular green alga Chlamydomonas reinhardtii that can be reduced by thioredoxin. These proteins were retained specifically on a thioredoxin affinity column made of a monocysteinic thioredoxin mutant able to form mixed disulfides with its targets. Of a total of 55 identified targets, 29 had been found previously in higher plants or Synechocystis, but 26 were new targets. Biochemical tests were performed on three of them, showing a thioredoxindependent activation of isocitrate lyase and isopropylmalate dehydrogenase and a thioredoxin-dependent deactivation of catalase that is redox insensitive in Arabidopsis. In addition, we identified a Ran protein, a previously uncharacterized nuclear target in a photosynthetic organism. The metabolic and evolutionary implications of these findings are discussed.O ur knowledge on redox regulation of various physiological processes through thiol-disulfide interchange with proteins of the thioredoxin (TRX) superfamily is rapidly progressing as genome-wide approaches and functional genomics studies are expanding. In the plant biology domain, thioredoxin-dependent regulation has been first discovered for chloroplastic enzymes involved in carbon assimilation (1). The completion of the sequencing of the Arabidopsis genome revealed that TRXs constituted a multigene family and led to the assumption that numerous TRX targets were still to be discovered (2-4). Thus, proteomic approaches aimed at identifying the largest possible number of TRX targets have been developed. The first attempts took advantage of the reaction mechanism of TRXs with their targets, in which a transient heterodisulfide forms between the reduced TRX and the oxidized protein, followed by the release of the reduced target due to the attack of the mixed disulfide by the second cysteine of TRX. Model studies showed that when this second cysteine was mutated, the heterodisulfide was stabilized (5, 6). This property was applied in vivo by transforming a TRX-null mutant yeast with a monocysteinic TRX and allowed isolating a peroxiredoxin (PRX) (7). Subsequently, monocysteinic TRX mutants were used in affinity chromatography to trap interacting proteins (8-11). Native TRX affinity columns also allowed retaining some targets by electrostatic interaction (12). Another technique was also developed that consists of a reduction of a crude soluble protein extract with reduced TRX followed by a separation of the proteins on a 2D gel after derivatization of the newly appeared thiols either with a fluorescent (13) or with a radioactive (14) reagent. In one case, both techniques have been applied in parallel (15), yielding similar results.Most of the disulfide proteomics have been led with higher plants: spinach (8, 10, 12), Arabidopsis (11, 14), or cereal grains (12). A single study was led with cyanobacteria and revealed targets mostly different from those of higher plants (16). The unicellular eukaryotic green alga Chlamydomonas reinhardtii possesses a TRX syste...

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Nuclear import and export of proteins in plants: a tool for the regulation of signalling

Cited by 59 publications

References 146 publications

ULTRAPETALA1encodes a SAND domain putative transcriptional regulator that controls shoot and floral meristem activity inArabidopsis

ULTRAPETALA1encodes a SAND domain putative transcriptional regulator that controls shoot and floral meristem activity inArabidopsis

A Novel WRKY Transcription Factor, SUSIBA2, Participates in Sugar Signaling in Barley by Binding to the Sugar-Responsive Elements of theiso1Promoter [W]

New thioredoxin targets in the unicellular photosynthetic eukaryote Chlamydomonas reinhardtii

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