Expression analysis of an Arabidopsis C2H2 zinc finger protein gene

Identification of histone deacetylase genes in Dendrobium officinale and their expression profiles under phytohormone and abiotic stress treatments

The deacetylation of core histones controlled by the action of histone deacetylases (HDACs) plays an important role in the epigenetic regulation of plant gene transcription. However, no systematic analysis of HDAC genes in Dendrobium officinale, a medicinal orchid, has been performed. In the current study, a total of 14 histone deacetylases in D. officinale were identified and characterized using bioinformatics-based methods. These genes were classified into RPD3/HDA1, SIR2, and HD2 subfamilies. Most DoHDAC genes in the same subfamily shared similar structures, and their encoded proteins contained similar motifs, suggesting that the HDAC family members are highly conserved and might have similar functions. Different cis-acting elements in promoters were related to abiotic stresses and exogenous plant hormones. A transient expression assay in onion epidermal cells by Agrobacterium-mediated transformation indicated that all of the detected histone deacetylases such as DoHDA7, DoHDA9, DoHDA10, DoHDT3, DoHDT4, DoSRT1 and DoSRT2, were localized in the nucleus. A tissue-specific analysis based on RNA-seq suggested that DoHDAC genes play a role in growth and development in D. officinale. The expression profiles of selected DoHDAC genes under abiotic stresses and plant hormone treatments were analyzed by qRT-PCR. DoHDA3, DoHDA8, DoHDA10 and DoHDT4 were modulated by multiple abiotic stresses and phytohormones, indicating that these genes were involved in abiotic stress response and phytohormone signaling pathways. These results provide valuable information for molecular studies to further elucidate the function of DoHDAC genes.

GLABROUS INFLORESCENCE STEMS3 (GIS3) regulates trichome initiation and development in Arabidopsis

Arabidopsis trichome formation is an excellent model for studying various aspects of plant cell development and cell differentiation. Our previous works have demonstrated that several C2H2 zinc finger proteins, including GIS, GIS2, ZFP5, ZFP6 and ZFP8, control trichome cell development through GA and cytokinin signalling in Arabidopsis. We identified a novel C2H2 zinc finger protein, GLABROUS INFLORESCENCE STEMS 3 (GIS3), which is a key factor in regulating trichome development in Arabidopsis. In comparison with wild-type plants, loss-of-function of GIS3 mutants exhibited a significantly decreased number of trichomes in cauline leaves, lateral branches, sepals of flowers, and main stems. Overexpression of GIS3 resulted in increased trichome densities in sepal, cauline leaves, lateral branches, main inflorescence stems and in the appearance of ectopic trichomes on carpels. The molecular and genetic analyses show that GIS3 acts upstream of GIS, GIS2, ZFP8 and the key trichome initiation factors, GL1 and GL3. Steroid-inducible gene expression analyses and chromatin immunoprecipitation (ChIP) experiments suggest that GIS and GIS2 are the direct target genes of GIS3.

Indigogenic substrates for detection and localization of enzymes

Indoxyl esters and glycosides are useful chromogenic substrates for detecting enzyme activities in histochemistry, biochemistry and bacteriology. The chemical reactions exploited in the laboratory are similar to those that generate indigoid dyes from indoxyl-beta-d-glucoside and isatans (in certain plants), indoxyl sulfate (in urine), and 6-bromo-2-S-methylindoxyl sulfate (in certain molluscs). Pairs of indoxyl molecules released from these precursors react rapidly with oxygen to yield insoluble blue indigo (or purple 6,6'-dibromoindigo) and smaller amounts of other indigoid dyes. Our understanding of indigogenic substrates was developed from studies of the hydrolysis of variously substituted indoxyl acetates for use in enzyme histochemistry. The smallest dye particles, with least diffusion from the sites of hydrolysis, are obtained from 5-bromo-, 5-bromo-6-chloro- and 5-bromo-4-chloroindoxyl acetates, especially the last of these three. Oxidation of the diffusible indoxyls to insoluble indigoid dyes must occur rapidly. This is achieved with atmospheric oxygen and an equimolar mixture of K(3)Fe(CN)(6) and K(4)Fe(CN)(6), which has a catalytic function. H(2)O(2) is a by-product of the oxidation of indoxyl by oxygen. In the absence of a catalyst, the indoxyl diffuses and is oxidized by H(2)O(2) (catalyzed by peroxidase-like proteins) in sites different from those of the esterase activity. The concentration of K(3)Fe(CN)(6)/K(4)Fe(CN)(6) in a histochemical medium should be as low as possible because this mixture inhibits some enzymes and also promotes parallel formation from the indoxyl of soluble yellow oxidation products. The identities and positions of halogen substituents in the indoxyl moiety of a substrate determine the color and the physical properties of the resulting indigoid dye. The principles of indigogenic histochemistry learned from the study of esterases are applicable to methods for localization of other enzymes, because all indoxyl substrates release the same type of chromogenic product. Substrates are commercially available for a wide range of carboxylic esterases, phosphatases, phosphodiesterases, aryl sulfatase and several glycosidases. Indigogenic methods for carboxylic esterases have low substrate specificity and are used in conjunction with specific inhibitors of different enzymes of the group. Indigogenic methods for acid and alkaline phosphatases, phosphodiesterases and aryl sulfatase generally have been unsatisfactory; other histochemical techniques are preferred for these enzymes. Indigogenic methods are widely used, however, for glycosidases. The technique for beta-galactosidase activity, using 5-bromo-4-chloroindoxyl-beta-galactoside (X-gal) is applied to microbial cultures, cell cultures and tissues that contain the reporter gene lac-z derived from E. coli. This bacterial enzyme has a higher pH optimum than the lysosomal beta-galactosidase of animal cells. In plants, the preferred reporter gene is gus, which encodes beta-glucuronidase activity and is also demonstrable by indigogenic histochemistry. Indoxyl substrates also are used to localize enzyme activities in non-indigogenic techniques. In indoxyl-azo methods, the released indoxyl couples with a diazonium salt to form an azo dye. In indoxyl-tetrazolium methods, the oxidizing agent is a tetrazolium salt, which is reduced by the indoxyl to an insoluble coloured formazan. Indoxyl-tetrazolium methods operate only at high pH; the method for alkaline phosphatase is used extensively to detect this enzyme as a label in immunohistochemistry and in Western blots. The insolubility of indigoid dyes in water limits the use of indigogenic substrates in biochemical assays for enzymes, but the intermediate indoxyl and leucoindigo compounds are strongly fluorescent, and this property is exploited in a variety of sensitive assays for hydrolases. The most commonly used substrates for this purpose are glycosides and carboxylic and phosphate esters of N-methylindoxyl. Indigogenic enzyme substrates are among many chromogenic reagents used to facilitate the identification of cultured bacteria. An indoxyl substrate must be transported into the organisms by a permease to detect intracellular enzymes, as in the blue/white test for recognizing E. coli colonies that do or do not express the lac-z gene. Secreted enzymes are detected by substrate-impregnated disks or strips applied to the surfaces of cultures. Such devices often include several reagents, including indigogenic substrates for esterases, glycosidases and DNAse.

A SUPERMAN-like gene is exclusively expressed in female flowers of the dioecious plant Silene latifolia

To elucidate the mechanism(s) underlying dioecious flower development, the present study analyzed a SUPERMAN (SUP) homolog, SlSUP, which was identified in Silene latifolia. The sex of this plant is determined by heteromorphic X and Y sex chromosomes. It was revealed that SlSUP is a single-copy autosomal gene expressed exclusively in female flowers. Introduction of a genomic copy of SlSUP into the Arabidopsis thaliana sup (sup-2) mutant complemented the excess-stamen and infertile phenotypes of sup-2, and the overexpression of SlSUP in transgenic Arabidopsis plants resulted in reduced stamen numbers as well as the suppression of petal elongation. During the development of the female flower in S. latifolia, the expression of SlSUP is first detectable in whorls 2 and 3 when the normal expression pattern of the B-class flowering genes was already established and persisted in the stamen primordia until the ovule had matured completely. In addition, significant expression of SlSUP was detected in the ovules, suggestive of the involvement of this gene in ovule development. Furthermore, it was revealed that the de-suppression of stamen development by infection of the S. latifolia female flower with Microbotryum violaceum was accompanied by a significant reduction in SlSUP transcript levels in the induced organs. Taken together, these results demonstrate that SlSUP is a female flower-specific gene and suggest that SlSUP has a positive role in the female flower developmental pathways of S. latifolia.

Zinc finger protein 1 (ThZF1) from salt cress (Thellungiella halophila) is a Cys-2/His-2-type transcription factor involved in drought and salt stress

Zinc finger proteins (ZFPs) play important roles in growth and development in both animals and plants. Recently, some Arabidopsis genes encoding distinct ZFPs have been identified. However, the physiological role of their homologues with putative zinc finger motif remains unclear. In the present study, a novel gene, ThZF1, was characterized from salt stressed cress (Thellungiella halophila, Shan Dong), encoding a functional transcription factor. ThZF1 contains two conserved C(2)H(2) regions and shares conserved domains, including DNA-binding motif, with Arabidopsis thaliana ZFP family members. The transcript of the ThZF1 gene was induced by salinity and drought. Transient expression analysis of ThZF1-GFP fusion protein revealed that ThZF1 was localized preferentially in nucleus. A gel-shift assay showed that ThZF1 specially bind to the wild-type (WT) EP2 element, a cis-element present in the promoter regions of several target genes regulated by ZFPs. Furthermore, a functional analysis demonstrated that ThZF1 was able to activate HIS marker gene in yeast. Finally, ectopic expression of ThZF1 in Arabidopsis mutant azf2 suggested that ThZF1 may have similar roles as Arabidopsis AZF2 in plant development as well as regulation of downstream gene.

Analysis of members of the Silene latifolia Cys2/His2 zinc-finger transcription factor family during dioecious flower development and in a novel stamen-defective mutant ssf1

Sex determination in dioecious Silene latifolia Poir. is governed by the inheritance of heteromorphic sex chromosomes. In male plants the Y chromosome influences two aspects of male organogenesis, the continued differentiation of stamen primordia and male fertility, and one aspect of female organogenesis, the arrest of development of the pistil. S. latifolia is susceptible to infection by the parasitic smut fungus Ustilago violacea, which induces stamen development in genetically female plants. Here we describe the identification and characterisation of a novel male mutant, short stamen filaments 1 (ssf1), defective in stamen differentiation. Although several independent studies have identified genes expressed during sex-determination in S. latifolia, analyses suggest that none of these encode regulatory proteins involved in the control of sex determination. We therefore isolated six S. latifolia cDNAs encoding members of a family of transcriptional regulators, the ZPT-type Cys2/His2 zinc-finger proteins that had previously shown to be co-ordinately regulated during stamen development in Petunia x hybrida hort. Vilm.-Andr. We have analysed the genomic organisation of these genes in male and female plants and their expression dynamics in male and female plants, in smut-infected female plants and in the ssf1 mutant. Our studies reveal expression patterns during development of the androecium that suggest a possible role for SlZPT2-1 in filament elongation and SlZPT4-1 in aspects of male fertility during stamen differentiation.

Ectopic expression of an Arabidopsis single zinc finger gene in tobacco results in dwarf plants

A survey of the Arabidopsis thaliana databases revealed that single C2H2 zinc finger protein genes comprise a large gene family (approximately 30 genes). No known phenotype has been associated with any of these genes except SUPERMAN. One of these genes, designated AtZFP10 (A. thaliana single zinc finger protein), was isolated by RT-PCR in the present study. The AtZFP10 gene was expressed at low levels in the flowers, axillary meristems and siliques, and at very low levels in the stems in Arabidopsis. Overexpression of the AtZFP10 gene driven by a constitutive promoter resulted in abnormal Arabidopsis plants and only one plant was recovered. Tobacco plants overexpressing the AtZFP10 gene displayed dwarfing, abnormal leaf phenotypes and early flowering that correlated with the level of expression of the AtZFP10 gene. No differences were observed in cell size between the AtZFP10 transgenic plants and the wild-type plants. Application of exogenous GA3 did not restore the wild-type phenotype, but it did reduce the dwarfing phenotype. Deletion of the leucine-rich region at the carboxyl terminus of the AtZFP10 gene resulted in transgenic plants that were not phenotypically different from wild-type plants suggesting a role for the leucine-rich region as essential for normal function.

TRM1, a YY1-like suppressor of rbcS-m3 expression in maize mesophyll cells

The genes rbcS and rbcL encode, respectively, the small and large subunits of the photosynthetic carbon dioxide fixation enzyme ribulose bisphosphate carboxylase/oxygenase. There is a single rbcL gene in each chloroplast chromosome; a family of rbcS genes is located in the nuclear genome. These two genes are not expressed in mesophyll cells but are in adjacent bundle-sheath cells of leaves of the C4 plant Zea mays. Two regions of the maize gene rbcS-m3 are required for suppressing expression in mesophyll cells. One region is just beyond the translation termination site in the 3' region, and the other is several hundred base pairs upstream of the transcription start site. A binding site for a protein with limited homology to the viral, yeast, and mammalian transcription repressor-activator YY1 (Yin-Yang I), has now been identified in the 3' region. A maize gene for a protein with zinc fingers homologous to those of YY1 has been isolated, characterized, and expressed in Escherichia coli. The gene is designated trm1 (transcription repressor-maize 1). The protein TRM1 binds to the YY1-like site and, in addition, TRM1 binds to two sequence regions in the 5' region of the gene that have no homology to the YY1 site. Mutagenesis or deletion of any of these three sequences eliminates repression of rbcS-m3 reporter genes in mesophyll cells.