Analysis of Brachypodium distachyon UVR8 reveals conservation in UV-B receptors

The Ultraviolet Resistance Locus 8 (UVR8) in plants recognizes Ultraviolet-B (UV-B) and plays a crucial role by regulating plant growth through a series of signal transduction events. However, the UVR8 in monocotyledon crops has not been systematically analyzed. We identified BdUVR8 (BRADI_3g45740) from the genome of Brachypodium distachyon, a relative of wheat, by analyzing the phylogenetic tree, gene expression pattern, detecting the accumulation of UV-B response metabolites, and check the phenotype recovery. The BdUVR8 protein sequence is similar to the known UVR8 of other species. The phylogenetic tree of UVR8 shows clear divergence between dicotyledons and monocotyledons. The expression analysis reveals that UV-B down-regulates BdUVR8 by 70% and up-regulates the chalcone synthase (BdCHS) gene 3.4-folds in B. distachyon. The pCAMBIA1300::BdUVR8-mCherry construct introduced into Arabidopsis uvr8 mutants shows that BdUVR8 protein localized in the cytoplasm translocates into the nucleus in response to UV-B irradiation. The introduction of BdUVR8 into uvr8 rescued the hypocotyl elongation by UV-B and restored the expression of HY5, Chalcone synthase, and Flavanone 3-hydroxylase as well as the accumulation of total flavonoids. Altogether, our results show that BdUVR8 is a photoreceptor that perceives UV-B in B. distachyon.

Risk factors for local recurrence and long term survival after minimally invasive intersphincteric resection for very low rectal cancer: Multivariate analysis in 161 patients

INTRODUCTION

Intersphincteric resection (ISR) is the ultimate anal-sparing technique as an alternative to abdominoperineal resection in selected patients. Oncological safety is still debated. This study analyses long-term oncological results and evaluates risk factors for local recurrence (LR) and overall survival (OS) after minimally-invasive ISR.

MATERIALS AND METHODS

Retrospective single-center data were collected from a prospectively maintained colorectal database. A total of 161 patients underwent ISR between 2008 and 2018. OS and local recurrence-free survival (LRFS) were assessed using Kaplan-Meier analysis (log-rank test). Risk factors for OS and LRFS were assessed with Cox-regression analysis.

RESULTS

Median follow-up was 55 months. LR occurred in 18 patients. OS and LRFS rates at 1, 3, and 5 years were 96%, 91%, and 80% and 96%, 89%, and 87%, respectively. Tumor size (p = 0.035) and clinical T-stage (p = 0.029) were risk factors for LRFS on univariate analysis. On multivariate analysis, tumor size (HR 2.546 (95% CI: 0.976-6.637); p = 0.056) and clinical T-stage (HR 3.296 (95% CI: 0.941-11.549); p = 0.062) were not significant. Preoperative CEA (p < 0.001), pathological T-stage (p = 0.033), pathological N-stage (p = 0.016) and adjuvant treatment (p = 0.008) were prognostic factors for OS on univariate analysis. Preoperative CEA (HR 4.453 (95% CI: 2.015-9.838); p < 0.001) was a prognostic factor on multivariate analysis.

CONCLUSIONS

This study confirms the oncological safety of minimally-invasive ISR for locally advanced low-lying rectal tumors when performed in experienced centers. Despite not a risk factor for LR, tumor size and, locally advanced T-stage with anterior involvement should be carefully evaluated for optimal surgical strategy. Preoperative CEA is a prognostic factor for OS.

Two guard cell mitogen-activated protein kinases, MPK9 and MPK12, function in methyl jasmonate-induced stomatal closure in Arabidopsis thaliana

Methyl jasmonate (MeJA) and abscisic acid (ABA) signalling cascades share several signalling components in guard cells. We previously showed that two guard cell-preferential mitogen-activated protein kinases (MAPKs), MPK9 and MPK12, positively regulate ABA signalling in Arabidopsis thaliana. In this study, we examined whether these two MAP kinases function in MeJA signalling using genetic mutants for MPK9 and MPK12 combined with a pharmacological approach. MeJA induced stomatal closure in mpk9-1 and mpk12-1 single mutants as well as wild-type plants, but not in mpk9-1 mpk12-1 double mutants. Consistently, the MAPKK inhibitor PD98059 inhibited the MeJA-induced stomatal closure in wild-type plants. MeJA elicited reactive oxygen species (ROS) production and cytosolic alkalisation in guard cells of the mpk9-1, mpk12-1 and mpk9-1 mpk12-1 mutants, as well in wild-type plants. Furthermore, MeJA triggered elevation of cytosolic Ca(2+) concentration ([Ca(2+)]cyt ) in the mpk9-1 mpk12-1 double mutant as well as wild-type plants. Activation of S-type anion channels by MeJA was impaired in mpk9-1 mpk12-1. Together, these results indicate that MPK9 and MPK12 function upstream of S-type anion channel activation and downstream of ROS production, cytosolic alkalisation and [Ca(2+)]cyt elevation in guard cell MeJA signalling, suggesting that MPK9 and MPK12 are key regulators mediating both ABA and MeJA signalling in guard cells.

First report: Robotic pelvic exenteration for locally advanced rectal cancer

AIM

The aim of this study was to present the feasibility and surgical outcome of robotic en bloc resection of the rectum and with prostate and seminal vesicle invaded by rectal cancer.

METHOD

The details of three consecutive cases involving male patients in their forties, with locally invasive low rectal cancers are presented. The da Vinci robotic system was used by experienced colorectal and urological surgeons to perform en bloc resection of the rectum, prostate and seminal vesicles.

RESULTS

In the first case, coloanal and vesico-urethral anastomoses were performed, and the second included an end colostomy and vesico-urethral anastomosis. The bladder and bulbar urethra were also removed en bloc in the third case, with robotic intracorporeal ileal conduit formation and end colostomy. There was no major complication postoperatively. In the second patient there was a minor leakage at the vesico-urethral anastomosis. The third was readmitted the following week with a urinary infection which settled with intravenous antibiotics. In the first case, the circumferential resection margin was microscopically positive but the patient is currently free of recurrence after 14 months. In the second and third cases, all margins were clear.

CONCLUSION

This the first report of the use of the da Vinci robotic system for pelvic exenteration in patients with locally advanced rectal cancer invading the prostate and seminal vesicles. The robot may have a potential role in selected patients requiring exenterative pelvic surgery particularly in men.

Two guard cell-preferential MAPKs, MPK9 and MPK12, regulate YEL signalling in Arabidopsis guard cells

We report that two mitogen-activated protein kinases (MAPKs), MPK9 and MPK12, positively regulate abscisic acid (ABA)-induced stomatal closure in Arabidopsis thaliana. Yeast elicitor (YEL) induced stomatal closure accompanied by intracellular reactive oxygen species (ROS) accumulation and cytosolic free calcium concentration ([Ca(2+) ]cyt ) oscillation. In this study, we examined whether these two MAP kinases are involved in YEL-induced stomatal closure using MAPKK inhibitors, PD98059 and U0126, and MAPK mutants, mpk9, mpk12 and mpk9 mpk12. Both PD98059 and U0126 inhibited YEL-induced stomatal closure. YEL induced stomatal closure in the mpk9 and mpk12 mutants but not in the mpk9 mpk12 mutant, suggesting that a MAPK cascade involving MPK9 and MPK12 functions in guard cell YEL signalling. However, YEL induced extracellular ROS production, intracellular ROS accumulation and cytosolic alkalisation in the mpk9, mpk12 and mpk9 mpk12 mutants. YEL induced [Ca(2+) ]cyt oscillations in both wild type and mpk9 mpk12 mutant. These results suggest that MPK9 and MPK12 function redundantly downstream of extracellular ROS production, intracellular ROS accumulation, cytosolic alkalisation and [Ca(2+) ]cyt oscillation in YEL-induced stomatal closure in Arabidopsis guard cells and are shared with ABA signalling.

Robotic total mesorectal excision: operative technique and review of the literature

In recent years, an increasing number of reports have been published on robotic colorectal surgery; this modality has also garnered an increasing amount of attention from the colorectal society. Most of the interest has been in robotic total mesorectal excision (TME) for rectal cancer. The purpose of this article is to briefly introduce our technique for total robotic TME and to review the recent literature regarding robotic TME for rectal cancer to summarize the current evidence on clinical and oncologic outcomes.

Dominant negative guard cell K+ channel mutants reduce inward-rectifying K+ currents and light-induced stomatal opening in arabidopsis

Inward-rectifying potassium (K+(in)) channels in guard cells have been suggested to provide a pathway for K+ uptake into guard cells during stomatal opening. To test the proposed role of guard cell K+(in) channels in light-induced stomatal opening, transgenic Arabidopsis plants were generated that expressed dominant negative point mutations in the K+(in) channel subunit KAT1. Patch-clamp analyses with transgenic guard cells from independent lines showed that K+(in) current magnitudes were reduced by approximately 75% compared with vector-transformed controls at -180 mV, which resulted in reduction in light-induced stomatal opening by 38% to 45% compared with vector-transformed controls. Analyses of intracellular K+ content using both sodium hexanitrocobaltate (III) and elemental x-ray microanalyses showed that light-induced K+ uptake was also significantly reduced in guard cells of K+(in) channel depressor lines. These findings support the model that K+(in) channels contribute to K+ uptake during light-induced stomatal opening. Furthermore, transpirational water loss from leaves was reduced in the K+(in) channel depressor lines. Comparisons of guard cell K+(in) current magnitudes among four different transgenic lines with different K+(in) current magnitudes show the range of activities of K+(in) channels required for guard cell K+ uptake during light-induced stomatal opening.

Dominant negative guard cell K+ channel mutants reduce inward-rectifying K+ currents and light-induced stomatal opening in arabidopsis

Inward-rectifying potassium (K+(in)) channels in guard cells have been suggested to provide a pathway for K+ uptake into guard cells during stomatal opening. To test the proposed role of guard cell K+(in) channels in light-induced stomatal opening, transgenic Arabidopsis plants were generated that expressed dominant negative point mutations in the K+(in) channel subunit KAT1. Patch-clamp analyses with transgenic guard cells from independent lines showed that K+(in) current magnitudes were reduced by approximately 75% compared with vector-transformed controls at -180 mV, which resulted in reduction in light-induced stomatal opening by 38% to 45% compared with vector-transformed controls. Analyses of intracellular K+ content using both sodium hexanitrocobaltate (III) and elemental x-ray microanalyses showed that light-induced K+ uptake was also significantly reduced in guard cells of K+(in) channel depressor lines. These findings support the model that K+(in) channels contribute to K+ uptake during light-induced stomatal opening. Furthermore, transpirational water loss from leaves was reduced in the K+(in) channel depressor lines. Comparisons of guard cell K+(in) current magnitudes among four different transgenic lines with different K+(in) current magnitudes show the range of activities of K+(in) channels required for guard cell K+ uptake during light-induced stomatal opening.

Dominant negative guard cell K+ channel mutants reduce inward-rectifying K+ currents and light-induced stomatal opening in arabidopsis

Inward-rectifying potassium (K+(in)) channels in guard cells have been suggested to provide a pathway for K+ uptake into guard cells during stomatal opening. To test the proposed role of guard cell K+(in) channels in light-induced stomatal opening, transgenic Arabidopsis plants were generated that expressed dominant negative point mutations in the K+(in) channel subunit KAT1. Patch-clamp analyses with transgenic guard cells from independent lines showed that K+(in) current magnitudes were reduced by approximately 75% compared with vector-transformed controls at -180 mV, which resulted in reduction in light-induced stomatal opening by 38% to 45% compared with vector-transformed controls. Analyses of intracellular K+ content using both sodium hexanitrocobaltate (III) and elemental x-ray microanalyses showed that light-induced K+ uptake was also significantly reduced in guard cells of K+(in) channel depressor lines. These findings support the model that K+(in) channels contribute to K+ uptake during light-induced stomatal opening. Furthermore, transpirational water loss from leaves was reduced in the K+(in) channel depressor lines. Comparisons of guard cell K+(in) current magnitudes among four different transgenic lines with different K+(in) current magnitudes show the range of activities of K+(in) channels required for guard cell K+ uptake during light-induced stomatal opening.

An mRNA cap binding protein, ABH1, modulates early abscisic acid signal transduction in Arabidopsis

The plant hormone abscisic acid (ABA) regulates important stress and developmental responses. We have isolated a recessive ABA hypersensitive mutant, abh1, that shows hormone specificity to ABA. ABH1 encodes the Arabidopsis homolog of a nuclear mRNA cap binding protein and functions in a heterodimeric complex to bind the mRNA cap structure. DNA chip analyses show that only a few transcripts are down-regulated in abh1, several of which are implicated in ABA signaling. Consistent with these results, abh1 plants show ABA-hypersensitive stomatal closing and reduced wilting during drought. Interestingly, ABA-hypersensitive cytosolic calcium increases in abh1 guard cells demonstrate amplification of early ABA signaling. Thus, ABH1 represents a modulator of ABA signaling proposed to function by transcript alteration of early ABA signaling elements.

Guard cell abscisic acid signalling and engineering drought hardiness in plants

Guard cells are located in the epidermis of plant leaves, and in pairs surround stomatal pores. These control both the influx of CO2 as a raw material for photosynthesis and water loss from plants through transpiration to the atmosphere. Guard cells have become a highly developed system for dissecting early signal transduction mechanisms in plants. In response to drought, plants synthesize the hormone abscisic acid, which triggers closing of stomata, thus reducing water loss. Recently, central regulators of guard cell abscisic acid signalling have been discovered. The molecular understanding of the guard cell signal transduction network opens possibilities for engineering stomatal responses to control CO2 intake and plant water loss.

Overexpression of the AtGluR2 gene encoding an Arabidopsis homolog of mammalian glutamate receptors impairs calcium utilization and sensitivity to ionic stress in transgenic plants

We have identified a homolog of the mammalian ionotropic glutamate receptor genes in Arabidopsis thaliana (AtGluR2). This gene was found to alter Ca2+ utilization when overexpressed in A. thaliana. These transgenic plants displayed symptoms of Ca2+ deficiency, including browning and death of the shoot apex, necrosis of leaf tips, and deformation of leaves. Supplementation with Ca2+ alleviated these phenotypes. Overall levels of Ca2+ in tissues of control plants were not significantly different from those of transgenic plants, suggesting that overexpression of the AtGluR2 gene did not affect Ca2+ uptake. However, the relative growth yield as a function of Ca2+ levels revealed that the critical deficiency content of Ca2+ in transgenic plants was three times higher than that of control plants. The transgenic plants also exhibited hypersensitivity to Na+ and K+ ionic stresses. The ion hypersensitivity was ameliorated by supplementation with Ca2+. The results showed that overexpression of the AtGluR2 gene caused reduced efficiency of Ca2+ utilization in the transgenic plants. The promoter of the AtGluR2 gene was active in vascular tissues, particularly in cells adjacent to the conducting vessels. This suggests that AtGluR2 encodes a functional channel that unloads Ca2+ from the xylem vessels. The results together suggest that appropriate expression of the AtGluR2 protein may play critical roles in Ca2+ nutrition by controlling the ion allocation among different Ca2+ sinks both during normal development and during adaptation to ionic stresses.

Cameleon calcium indicator reports cytoplasmic calcium dynamics in Arabidopsis guard cells

Cytoplasmic free calcium ([Ca2+]cyt) acts as a stimulus-induced second messenger in plant cells and multiple signal transduction pathways regulate [Ca2+]cyt in stomatal guard cells. Measuring [Ca2+]cyt in guard cells has previously required loading of calcium-sensitive dyes using invasive and technically difficult micro-injection techniques. To circumvent these problems, we have constitutively expressed the pH-independent, green fluorescent protein-based calcium indicator yellow cameleon 2.1 in Arabidopsis thaliana (Miyawaki et al. 1999; Proc. Natl. Acad. Sci. USA 96, 2135-2140). This yellow cameleon calcium indicator was expressed in guard cells and accumulated predominantly in the cytoplasm. Fluorescence ratio imaging of yellow cameleon 2.1 allowed time-dependent measurements of [Ca2+]cyt in Arabidopsis guard cells. Application of extracellular calcium or the hormone abscisic acid (ABA) induced repetitive [Ca2+]cyt transients in guard cells. [Ca2+]cyt changes could be semi-quantitatively determined following correction of the calibration procedure for chloroplast autofluorescence. Extracellular calcium induced repetitive [Ca2+]cyt transients with peak values of up to approximately 1.5 microM, whereas ABA-induced [Ca2+]cyt transients had peak values up to approximately 0.6 microM. These values are similar to stimulus-induced [Ca2+]cyt changes previously reported in plant cells using ratiometric dyes or aequorin. In some guard cells perfused with low extracellular KCl concentrations, spontaneous calcium transients were observed. As yellow cameleon 2.1 was expressed in all guard cells, [Ca2+]cyt was measured independently in the two guard cells of single stomates for the first time. ABA-induced, calcium-induced or spontaneous [Ca2+]cyt increases were not necessarily synchronized in the two guard cells. Overall, these data demonstrate that that GFP-based cameleon calcium indicators are suitable to measure [Ca2+]cyt changes in guard cells and enable the pattern of [Ca2+]cyt dynamics to be measured with a high level of reproducibility in Arabidopsis cells. This technical advance in combination with cell biological and molecular genetic approaches will become an invaluable tool in the dissection of plant cell signal transduction pathways.

A Brassica cDNA clone encoding a bifunctional hydroxymethylpyrimidine kinase/thiamin-phosphate pyrophosphorylase involved in thiamin biosynthesis

We report the characterization of a Brassica napus cDNA clone (pBTHI) encoding a protein (BTHI) with two enzymatic activities in the thiamin biosynthetic pathway, thiamin-phosphate pyrophosphorylase (TMP-PPase) and 2-methyl-4-amino-5-hydroxymethylpyrimidine-monophosphate kinase (HMP-P kinase). The cDNA clone was isolated by a novel functional complementation strategy employing an Escherichia coli mutant deficient in the TMP-PPase activity. A biochemical assay showed the clone to confer recovery of TMP-PPase activity in the E. coli mutant strain. The cDNA clone is 1746 bp long and contains an open reading frame encoding a peptide of 524 amino acids. The C-terminal part of BTH1 showed 53% and 59% sequence similarity to the N-terminal TMP-PPase region of the bifunctional yeast proteins Saccharomyces THI6 and Schizosaccharomyces pombe THI4, respectively. The N-terminal part of BTH1 showed 58% sequence similarity to HMP-P kinase of Salmonella typhimurium. The cDNA clone functionally complemented the S. typhimurium and E. coli thiD mutants deficient in the HMP-P kinase activity. These results show that the clone encodes a bifunctional protein with TMP-PPase at the C-terminus and HMP-P kinase at the N-terminus. This is in contrast to the yeast bifunctional proteins that encode TMP-PPase at the N-terminus and 4-methyl-5-(2-hydroxyethyl)thiazole kinase at the C-terminus. Expression of the BTH1 gene is negatively regulated by thiamin, as in the cases for the thiamin biosynthetic genes of microorganisms. This is the first report of a plant thiamin biosynthetic gene on which a specific biochemical activity is assigned. The Brassica BTH1 gene may correspond to the Arabidopsis TH-1 gene.

AtKUP1: an Arabidopsis gene encoding high-affinity potassium transport activity

Because plants grow under many different types of soil and environmental conditions, we investigated the hypothesis that multiple pathways for K+ uptake exist in plants. We have identified a new family of potassium transporters from Arabidopsis by searching for homologous sequences among the expressed sequence tags of the GenBank database. The deduced amino acid sequences of AtKUP (for Arabidopsis thaliana K+ uptake transporter) cDNAs are highly homologous to the non-plant Kup and HAK1 potassium transporters from Escherichia coli and Schwanniomyces occidentalis, respectively. Interestingly, AtKUP1 and AtKUP2 are able to complement the potassium transport deficiency of an E. coli triple mutant. In addition, transgenic Arabidopsis suspension cells overexpressing AtKUP1 showed increased Rb+ uptake at micromolar concentrations with an apparent K(m) of approximately 22 microM, indicating that AtKUP1 encodes a high-affinity potassium uptake activity in vivo. A small, low-affinity Rb+ uptake component was also detected in AtKUP1-expressing cells. RNA gel blot analysis showed that the various members of the AtKUP family have distinct patterns of expression, with AtKUP3 transcript levels being strongly induced by K+ starvation. It is proposed that plants contain multiple potassium transporters for high-affinity uptake and that the AtKUP family may provide important components of high- and low-affinity K+ nutrition and uptake into various plant cell types.

AtKUP1: an Arabidopsis gene encoding high-affinity potassium transport activity

Because plants grow under many different types of soil and environmental conditions, we investigated the hypothesis that multiple pathways for K+ uptake exist in plants. We have identified a new family of potassium transporters from Arabidopsis by searching for homologous sequences among the expressed sequence tags of the GenBank database. The deduced amino acid sequences of AtKUP (for Arabidopsis thaliana K+ uptake transporter) cDNAs are highly homologous to the non-plant Kup and HAK1 potassium transporters from Escherichia coli and Schwanniomyces occidentalis, respectively. Interestingly, AtKUP1 and AtKUP2 are able to complement the potassium transport deficiency of an E. coli triple mutant. In addition, transgenic Arabidopsis suspension cells overexpressing AtKUP1 showed increased Rb+ uptake at micromolar concentrations with an apparent K(m) of approximately 22 microM, indicating that AtKUP1 encodes a high-affinity potassium uptake activity in vivo. A small, low-affinity Rb+ uptake component was also detected in AtKUP1-expressing cells. RNA gel blot analysis showed that the various members of the AtKUP family have distinct patterns of expression, with AtKUP3 transcript levels being strongly induced by K+ starvation. It is proposed that plants contain multiple potassium transporters for high-affinity uptake and that the AtKUP family may provide important components of high- and low-affinity K+ nutrition and uptake into various plant cell types.

Resistance to tobamoviruses in transgenic tobacco plants expressing the coat protein gene of pepper mild mottle virus (Korean isolate)

Red pepper, one of the most important vegetable crops in Korea, is severely affected by viral diseases causing 20-50% reduction in product yield. A pepper strain of tobacco mosaic virus (TMV-p) is the most common virus in red pepper. To study the molecular structure of the TMV-p virus, we generated cDNA clones of the viral genome. Partial sequencing of a few cDNA clones revealed that TMV-p shares a 98% identity at the nucleotide level with the Spanish isolate of pepper mild mottle virus (PMMV-s). This suggests that TMV-p should be reclassified as the Korean isolate of PMMV (PMMV-k). The coat protein (CP) gene together with the 3' untranslated region of the PMMV-k virus was obtained by reverse transcriptase-polymerase chain reaction (RT-PCR) using oligomers deduced from the sequence of PMMV-s. The sequence analysis of the CP gene and the 3' untranslated region further confirmed that PMMV-k is highly related to PMMV-s. The CP gene and the 3' untranslated region of PMMV-k were cloned into a plant expression vector and the construct was introduced into tobacco plants. The transgenic plants expressing the PMMV-k CP gene were delayed in developing systemic disease or failed to develop symptoms at all after inoculation with PMMV-k. Delay of symptoms was also observed when the plants were inoculated with TMV-OM which shares a 74% homology with PMMV-k in the amino acid sequence of the CP region. In a local lesion host, the CP expressing plants exhibited a greatly reduced number of necrotic lesions as compared to control plants after inoculation with TMV-OM. Our results show that CP-mediated viral resistance is readily applicable in the case of PMMV-k and can provide resistance to other viruses in the tobamovirus group.

Identification of a receptor-like protein kinase gene rapidly induced by abscisic acid, dehydration, high salt, and cold treatments in Arabidopsis thaliana

A cDNA clone for a receptor-like protein kinase gene (RPK1) was isolated from Arabidopsis thaliana. The clone is 1952 bp long with 1623 bp of an open reading frame encoding a peptide of 540 amino acids. The deduced peptide (RPK1) contains four distinctive domains characteristic of receptor kinases: (a) a putative amino-terminal signal sequence domain; (b) a domain with five extracellular leucine-rich repeat sequences; (c) a membrane-spanning domain; and (d) a cytoplasmic protein kinase domain that contains all of the 11 subdomains conserved among protein kinases. The RPK1 gene is expressed in flowers, stems, leaves, and roots. Expression of the RPK1 gene is induced within 1 h after treatment with abscisic acid (ABA). The gene is also rapidly induced by several environmental stresses such as dehydration, high salt, and low temperature, suggesting that the gene is involved in a general stress response. The dehydration-induced expression is not impaired in aba-1, abi1-1, abi2-1, and abi3-1 mutants, suggesting that the dehydration-induced expression of the RPK1 gene is ABA-independent. A possible role of this gene in the signal transduction pathway of ABA and the environmental stresses is discussed.

Insulin-induced maturation of Xenopus oocytes is inhibited by microinjection of a Brassica napus cDNA clone with high similarity to a mammalian receptor for activated protein kinase C

A cDNA clone encoding a WD-40 repeat protein (BGB1) was characterized in Brassica napus L. The clone contained an open reading frame of 327 amino acid residues almost entirely composed of seven segments of WD-40 repeats. Among the WD-40 repeat proteins, BGB1 showed high similarity (63% identity) to a rat intracellular receptor for protein kinase C (RACK1) that functions in the translocation of activated protein kinase C (PKC) from the cytosolic fraction to the membrane fraction. BGB1 also had two sequence motifs involved in binding of RACK1 to PKC. The cDNA clone, when carried in a Xenopus oocyte expression vector and injected into Xenopus laevis oocytes, inhibited insulin-induced maturation of the oocytes, a PKC-mediated pathway, and this inhibition was accompanied by reduction of PKC in the membrane fraction, as in the case of mammalian RACKs. The data show that BGB1 shares some common functional characteristics with the mammalian RACK1 along with the structural similarity, suggesting that a mammalian RACK1-related cellular process might be operating in plants. Southern blot analyses of the genome of B. napus and Arabidopsis thaliana (L.) Heynh. revealed that BGB1-related genes constitute a small multigene family in both species. An approximately 1.4-kb transcript was constitutively expressed in all organs examined.

Evaluation of 515 expressed sequence tags obtained from guard cells of Brassica campestris

As an attempt to examine the transcripts expressed in a single cell type and to unveil the physiology of guard cells at the molecular level, we generated 515 expressed sequence tags (ESTs) from a directional cDNA library constructed from guard-cell protoplasts of Brassica campestris L. ssp. pekinensis. A comparative analysis of the guard-cell ESTs against the National Center for Biotechnological Information non-redundant protein database revealed that 133 ESTs (26%) have significant similarity to protein coding sequences in the database. Among them were 35 clones related to genes that have not yet been identified in higher plants. Analysis of RNA gel blots of 14 database-matched clones revealed that five clones harbor the sequences for mRNAs expressed most abundantly in guard cells, one of them detecting an mRNA with highly preferential expression in guard cells. Functional categorization of the putatively identified guard-cell ESTs showed, when compared with maize leaf ESTs, that guard cells expressed a higher proportion of signal transduction components and a lower proportion of structural or photosynthetic genes, as is consistent with the roles of guard cells.

Rapid and transient induction of calmodulin-encoding gene(s) of Brassica napus by a touch stimulus

A cDNA clone for a calmodulin gene (bcm1) was isolated from Brassica napus. The clone encodes a peptide identical to the calmodulins encoded by the Arabidopsis ACaM-2, -3 and -5 cDNA clones and shows 92% nucleotide sequence identity to the ACaM-3 clone. Northern blot analysis shows that a single band of transcript is detected in all organs examined and most abundantly in the root with the 3' untranslated sequence probe. In addition, the transcript level increases rapidly (within 30 min) after wound or touch stimulation and starts to decline in 3 hr, suggesting that calmodulin may be involved in the responses to these stimuli in Brassica napus. The gene is a member of a multigene family in Brassica napus.

Frequent in-frame length variations are found in the diverged simple repeat sequences of the protein-coding regions of two putative protein kinase genes of Brassica napus

Two putative protein kinase cDNA clones were isolated from Brassica napus by screening with a putative protein kinase cDNA clone of Arabidopsis thaliana. The deduced amino acid sequences show a distinct modular composition, consisting of a possible protein kinase catalytic region at the amino terminus and a highly acidic region encoded from diverged simple repeat sequences at the carboxy terminus. Comparison of the nucleotide sequences encoding this acidic region revealed a high rate of in-frame length variation, while preserving the acidic characteristics. Similar variation is also found in the noncoding regions of these clones.

Functional complementation of a yeast vesicular transport mutation ypt1-1 by a Brassica napus cDNA clone encoding a small GTP-binding protein

A cDNA clone (bra) encoding a small GTP-binding protein was isolated from Brassica napus by screening a root cDNA library with a degenerate oligonucleotide probe that corresponds to a highly conserved GTP-binding domain of the Ras superfamily. Sequence analysis shows that the clone contains an open reading frame of 219 amino acid residues with the estimated molecular mass of 24379 Da and this coding region contains all the conserved motifs of the Ras superfamily. The deduced amino acid sequence of the bra gene is most closely related to the Ypt/Rab family that functions in the vesicular transport (46% and 47% amino acid identity to the yeast Ypt1 and to the human Rab1, respectively) and is more distantly related to the other Ras-related families. The protein encoded by the bra gene, when expressed in Escherichia coli, shows the ability to bind GTP. Furthermore, when the bra gene is introduced into Saccharomyces cerevisiae under the regulation of the yeast GAL1 promoter, the gene can complement the temperature-sensitive yeast mutation ypt1-1 that has defects in vesicular transport function. The amino acid sequence similarity and the functional complementation of the yeast mutation suggest that this gene is likely to be involved in the vesicular transport in plants. Genomic Southern analysis shows that this gene is a member of a small gene family in Brassica napus.

Isolation and characterization of two cDNA clones that are rapidly induced during the wound response of Arabidopsis thaliana

Differential screening of a cDNA library of Arabidopsis thaliana constructed from the plant tissues harvested 1 h after wounding resulted in isolation of 2 wound-inducible cDNA clones. Kinetic analysis revealed that the corresponding genes are rapidly induced upon wounding. Expression of these clones reached the maximum level around 1-1.5 h after wounding and then were progressively reduced. The time by which expression returned to the control level was around 3 h after wounding. Partial sequence analysis revealed that the two clones are highly homologous to the S-adenosylmethionine synthetase and the glutathione-S-transferase gene, respectively.

Generation of expressed sequence tags of random root cDNA clones of Brassica napus by single-run partial sequencing

Two hundred thirty-seven expressed sequence tags (ESTs) of Brassica napus were generated by single-run partial sequencing of 197 random root cDNA clones. A computer search of these root ESTs revealed that 21 ESTs show significant similarity to the protein-coding sequences in the existing data bases, including five stress- or defense-related genes and four clones related to the genes from other kingdoms. Northern blot analysis of the 10 data base-matched cDNA clones revealed that many of the clones are expressed most abundantly in root but less abundantly in other organs. However, two clones were highly root specific. The results show that generation of the root ESTs by partial sequencing of random cDNA clones along with the expression analysis is an efficient approach to isolate genes that are functional in plant root in a large scale. We also discuss the results of the examination of cDNA libraries and sequencing methods suitable for this approach.

Two putative protein kinases from Arabidopsis thaliana contain highly acidic domains

Two cDNA clones (ASK1 and ASK2) for plant protein kinases were cloned from Arabidopsis thaliana by screening cDNA libraries with a degenerate oligonucleotide probe that corresponds to a highly conserved motif among protein kinases. Sequence analysis shows that the clones contain open reading frames that encode 41.2 kDa (ASK1) and 40.1 kDa (ASK2) proteins, respectively. These coding regions contain all the conserved motifs of protein kinases. Structural analysis of the coding regions revealed that the two protein kinase genes share high sequence similarity to each other (76.6% identity). The catalytic domain located in the amino terminal region is most similar to the calcium/calmodulin-dependent protein kinase subfamily (47.2% to 54.2% similarity) and the SNF1 kinase subfamily (48.1% to 53.3% similarity). However, the carboxy terminal regions contain distinctive stretches of 21 (ASK1) and 19 (ASK2) acidic amino acids. These clones are the first report of protein kinases with such acidic amino acid regions. The transcripts of both genes are most abundant in leaf but are also expressed in other organs. The expression of the two genes is highly affected by light regime.