dad-1, A Putative Programmed Cell Death Suppressor Gene in Rice

The human dad-1 cDNA homolog was isolated from rice plants.The amino acid sequence of the predicted protein product iswell conserved in both animals and plants. This rice dad-1 homologcan rescue the temperature-sensitive dad-1 mutants of hamstercells from apoptotic death, suggesting that the rice dad-1 homologalso functions as a suppressor for programmed cell death. (Received December 24, 1997; Accepted January 27, 1997)     

Interannual variability in a predator-prey interaction: climate, chaetognaths and copepods in the southeastern Bering Sea

The interaction of the chaetognath Sagitta elegans with thecopepod community of the southeast Bering Sea middle shelf wasexamined in relation to environmental conditions during 1995–1999.Predation impact was estimated for 2 years, 1995 and 1997, usinggut content analysis, experimentally derived digestion time(DT) and abundances of chaetognaths and prey. Pseudocalanusconcentrations correlated with water temperature and Calanusmarshallae with sea ice extent. Sagitta elegans were less abundantbut individuals were larger in 1995, when C. marshallae predominated,compared to 1997, when Pseudocalanus and Acartia were the primaryprey. Predation by S. elegans removed <1% standing stockday^–1 of Pseudocalanus or C. marshallae in 1995 and 1.7to 2.3% of Pseudocalanus in 1997. The percent of the copepodcommunity biomass required by chaetognaths was estimated tobe <1% in 1995 compared with 8–12% in 1997. Calanusmarshallae may be more vulnerable than Pseudocalanus to cumulativepredation effects because of its reproductive strategy. Theeffect of chaetognath predation on the copepod community dependson which copepod species is predominant and its susceptibilityto cumulative predation effects, as well as on daily predationimpact, both of which varied between years with different climaticconditions.     

Expression of Plasma Membrane Water Channel Genes under Water Stress in Nicotiana excelsior

Deduced amino acid sequences encoded by the cDNAs related tothe MIP gene family from Nicotiana excelsior were characterized.Phylogenetic characterization of the products of correspondinggenes named NeMip1, NeMip2, and NeMip3 strongly suggested thatthey are water channel proteins localized in the plasma membrane.Organ specificity of the gene expression was examined in leaves,roots, and reproductive organs. NeMip1 was expressed in rootsand reproductive organs; however, it was hardly detectable inleaves. Two other genes, NeMip2 and NeMip3, were expressed inall of organs examined. mRNA accumulation from the genes wasinvestigated in leaves under salt- and drought-stresses. Theresults demonstrated that mRNA accumulation from all three genesincreased under salt- and drought-stresses within one day. However,they showed different accumulation patterns. In addition totheir up-reg-ulation under salt- and drought-stresses, dailychanges in NeMip2 and NeMip3 mRNA accumulation was observedunder unstressed conditions in leaves. (Received May 2, 1997; Accepted September 3, 1997)     

Isolation and Characterization of cDNA Clones with Enhanced Expression in Tobacco Plants Expressing the Rice Homeobox Gene, OSH1

We have used subtractive hybridization to isolate cDNA cloneswhose expression were up-regulated in transgenic tobacco ectopicallyexpressing the rice homeobox gene, OSH1. Thirty-nine distinctcDNA clones, which we term HRGs (Homeobox Regulated Genes),were identified. Some of them were specifically expressed intransformants, indicating that their expression was possiblyregulated by transgene. (Received January 9, 1997; Accepted March 8, 1997)     

The RHG Gene Is Involved in Root and Hypocotyl Gravitropism in Arabidopsis thaliana

In higher plants, shoots show negative gravitropism and rootsshow positive gravitropism. To elucidate the molecular mechanismsof root and hypocotyl gravitropism, we segregated the secondmutation from the original phyB-1 mutant line which impairedboth root and hypocotyl gravitropism and characterized thisnovel mutation named rhg (for root and hyzypocotyl gravitropism).The rhg is a single recessive nuclear mutation and it is mappedon the lower part of the chromosome 1. Analyses on the gravitropicresponses of the rhg mutant indicate that root and hypocotylgravitropism are severely impaired but inflorescence stem gravitropismis not affected by the rhg mutation. In the rhg mutant seedlings,amyloplasts (statoliths for gravity-perception) were presentin the presumptive statocytes of roots and hypocotyls. Phototropismby roots and hypocotyls was not impaired in the rhg mutant.These results suggest that the RHG gene product probably actson the gravity-perception and/or the gravity-signal transductionin root and hypocotyl gravitropism. This is the first reportabout the genetic locus specifically involved in both root andhypocotyl gravitropism but not inflorescence stem gravitropism,supporting our hypothesis that the mechanisms of gravitropismare genetically different between hypocotyls and inflorescencestems. (Received March 11, 1997; Accepted April 17, 1997)     

Distribution of Calanus species in Kongsfjorden, a glacial fjord in Svalbard

The distribution of Calanus species was investigated in Kongsfjordenin summer of 1996 and 1997. In both years Calanus finmarchicusand Calanus glacialis dominated, although the boreal C. finmarchicuswas more abundant than the Arctic C. glacialis in 1997. Thiscoincided with a 2°C higher water temperature at 50 m in1997, indicating stronger influence of Atlantic origin waterthat year. Advected Calanus finmarchicus occurred in deep andsubsurface layers of the outer fjord in 1996 (200 ind. m^-3,mainly CIII). A less abundant local population aggregated insurface layers of the inner fjord (100 ind. m^-3). Similarly,advected C. finmarchicus occurred in subsurface layers in 1997(446 ind. m^-3, mainly CIII and CIV) and a local population insurface layers (183 ind. m^-3, mainly CI). Calanus glacialisin 1996 aggregated as CII and CIII in the deep layers of theouter fjord (272 ind. m^-3), whereas CIII–CV were abundant(216 ind. m^-3) in cold surface waters of the inner fjord. In1997 C. glacialis (mostly CIII–CV) was more abundant inthe outer than in the inner part of the fjord (40 and 192 ind.m^-3, respectively). Within Kongsfjorden, Calanus finmarchicusneeds one year to complete its life cycle, whereas Calanus glacialisneeds two. Calanus hyperboreus seems to be an expatriate inthe fjord system.     

Zinc Deficiency Affects the Levels of Endogenous Gibberellins in Zea mays L.

Zinc deficiency in Zea mays L. markedly reduced the level ofGA₁, but not GA₂₀, suggesting blockage of 3rß-hy-droxylation.The level of IAA was also decreased although not as markedly.Castasterone was affected less than IAA by zinc deficiency. (Received February 24, 1997; Accepted June 24, 1997)     

The Spirulina platensis Adenylate Cyclase Gene, cyaC, Encodes a Novel Signal Transduction Protein

A cyaC gene encoding an adenylate cyclase of the filamentouscyanobacterium Spirulina platensis was se-quenced. The predictedamino acid sequence of the C-ter-minal region of cyaC is similarto the catalytic domains of adenylate cyclases in other cyanobacteriaand eukaryotes. The sequences of other regions are similar tothose of proteins consisting of the bacterial two-componentsignal transduction system: the sensory kinase and the responseregulator. The predicted gene product of cyaC contains, fromthe N-terminal end, a receiver domain of the response regulatorprotein (Rl), a domain similar to the ETR1 of Arabi-dopsis thaliana,a transmitter domain of the sensory kinase protein, a receiverdomain of the response regulator protein (R2), and a catalyticdomain of adenylate cyclase. The cyaC gene was expressed asan affinity-tagged protein in Escherichia coli, and the recombinantprotein was purified. The purified protein had adenylate cyclaseactivity which was activated by Mn²+. The results of Westernblotting using an anti-CyaC antiserum and the S. platensis cellextract confirmed that cyaC gene is expressed in S. platensis (Received February 27, 1997; Accepted April 26, 1997)     

First Nuclear DNA C-values for 25 Angiosperm Families

DNA amount is a widely used biodiversity character. As knownDNA C-values represent the global angiosperm flora poorly, bettercoverage of taxonomic groups is needed, including at the familiallevel. A workshop, sponsored byAnnals of Botany , was held atthe Royal Botanic Gardens, Kew in 1997. Its key aim was to identifymajor gaps in our knowledge of plant DNA C-values and recommendtargets for new work to fill them by international collaboration.In 1997 C-values were known for approx. 150 families, meaningthere was no estimate for most angiosperm families (approx 68%).The workshop recommended a goal of complete familial representationby 2002, as a main target for angiosperms. Bennett et al. (Annalsof Botany86: 859–909, 2000) presented a fifth supplementarylist of angiosperm C-values from 70 original sources which includedfirst C-values for 691 species. Only 12 (1.7%) of these werefirst C-values for unrepresented families, so the need to improvefamilial representation was substantially unmet. We began newwork to address this in September 1999, and now report firstDNA C-values for 25 angiosperm families. Such targeting seemsessential to achieve the goal of familial coverage set by the1997 workshop within 5 years. 4C values range from 0.67 pg (similartoArabidopsis thaliana ) in Amoreuxia wrightii(Cochlospermaceae)to 7.49 pg in Deutzia prunifolia(Hydrangeaceae). These datasupport the view that ancestral angiosperms almost certainlyhad small genomes (defined as 1C     

Calcium-Dependent and -Independent Phosphoenolpyruvate Carboxylase Kinases in Sorghum Leaves: Further Evidence for the Involvement of the Calcium-Independent Protein Kinase in the in situ Regulatory Phosphorylation of C4 Phosphoenolpyruvate Carboxylase

Calcium-dependent phosphoenolpyruvate carboxylase protein kinasewas copurified with C₄ phosphoenolpyruvate carboxylase (C₄ PEPC)from illuminated Sorghum leaves during purification by variousprocedures. Isolated mesophyll cell protoplasts contained bothcalcium-dependent and -independent protein kinases. The latterwas induced by light and weak bases and was found to be themajor protein kinase phosphorylating C₄ PEPC in the mesophyll. (Received July 29, 1997; Accepted November 28, 1997)     

The role of faecal material in the particulate organic carbon flux in the northern Humboldt Current, Chile (23{degrees}S), before and during the 1997-1998 El Nino

Sedimentation rates of faecal material, phytoplankton and microzooplanktonand production rates of faecal material from crustaceans andpelagic tunicates were estimated during the austral summer andwinter 1997, and summer 1998, in the northern Humboldt Current(23°S, off Antofagasta, Chile). Sampling periods coveredpre-El Niño (January 1997) and El Niño 1997–98(July 1997 and January 1998). Samples were collected using floatingsediment traps deployed at 65, 100, 200 and 300 m depth in oceanicand coastal areas. Sedimentation rates during January 1997 were,on average, 152 ± 23 and 85 ± 57 mg C m^–2day^–1 at 65 and 300 m depth, respectively. During July,these rates averaged 93 ± 56 mg C m^–2 day^–1at 65 m depth and 35 ± 12 mg C m^–2 day^–1at 300 m depth, while in January 1998 they were 98 and 109 ±37 mg C m^–2 day^–1 at 65 and 200 m depth, respectively.Recognizable faecal material made up the bulk of the sedimentingmatter, accounting for 8 ± 5% (n = 14), 31 ± 26%(n = 16) and 8 ± 5% (n = 5) of the average total organiccarbon recorded from all sediment trap samples collected duringJanuary and July 1997 and January 1998, respectively. However,at300 m depth, the contribution of recognizable faecal materialto total sedimented organic carbon increased to 43 ±33% (n = 4) during July 1997. The remaining sedimenting particlesconsisted mainly of tintinnids, crustacean exuviae, heterotrophicdinoflagellates (both thecated and athecated) and diatom cells.During this study, we estimated that only a minor fraction (average± SD = 5 ± 8%) of the copepod faecal materialproduced within the photic zone sedimented down to 300 m depth,suggesting an efficient recycling within the overlaying watercolumn. On the other hand, an important fraction (47 ±30%) of the euphausiid faecal strings was collected in the 300m depth trap, suggesting that this material would enhance thedownward flux of particulate organic matter (POC). POC fluxesto 65 and 300 m depth traps were in the range of 4–20%and 3–8% of the estimated primary production during thewhole study period. It is postulated that the overall verticalflux of particulates and, in particular, faecal pellets wasdetermined by a combination of three factors. The first wasthe composition of the zooplankton assemblages in the studyarea. When the dominant group was calanoid copepods, their faecesseemed to contribute poorly to the vertical flux of particulates.On the other hand, when the dominant group was euphausiids,a significant proportion of their faecal material was collectedin the sediment trap located at 300 m depth. The second wasthe relatively high abundance of cyclopoid copepods from thegenera Oncaea, Corycaeus and Oithona, which are reported tofeed on aggregates of phytodetritus and faecal pellets producedby calanoid copepods, suggesting that they may act as a naturalfilter to sedimenting particulates. The third was the compositionand size spectrum of the phyto- and microzooplankton assemblageswhich are potential food sources for the meso- and macrozooplankton.These factors were partially modulated by both the 1997–1998El Niño and seasonality.     

First Nuclear DNA C-values for Another 25 Angiosperm Families

Nuclear DNA C-value is an important genomic biodiversity characterwith many uses. An international workshop sponsored by Annalsof Botany and held at the Royal Botanic Gardens, Kew, UK, in1997 identified major gaps in our knowledge of plant DNA C-valuesand recommended targets for new work. Improved taxonomic coveragewas highlighted as a key need for angiosperms, especially atthe familial level. In 1997 C-values were known for only approx.32% of angiosperm families; a goal of complete familial representationby 2002 was recommended. A review published in 2000 (Bennettet al.;Annals of Botany86: 859–909) noted poor progresstowards this aim: of the 691 first C-values for species only12 (1.7%) were for unrepresented families. We began new workto address this in 1999, reporting first DNA C-values for 25angiosperm families in 2001 (Hanson et al.;Annals of Botany87:251–258). Here we report first DNA C-values for a further25 angiosperm families, increasing familial coverage in angiospermsto approx. 45%. Such targeting remains essential to approachthe goal set by the 1997 workshop of familial coverage for angiospermswithin 5 years. The 4C DNA amounts presented here range from0.76 pg (similar toArabidopsis thaliana ) in Roridula gorgonias(Roridulaceae)to 29.74 pg in Gunnera manicata(Gunneraceae). 1C values were< 3.5 pg in 23 of the 25 families; these data provide furthersupport for the view that ancestral angiosperms almost certainlyhad small genomes (defined as 1C     

Gibberellin A3 Causes a Decrease in the Accumulation of mRNA for ACC Oxidase and in the Activity of the Enzyme in Azuki Bean (Vigna angularis) Epicotyls

Differential screening, aimed at the isolation of cDNA clonesof mRNAs whose accumulation is influenced by GA₃, resulted inthe isolation of a cDNA clone of an mRNA whose level was decreasedby GA₃ in segments of epicotyls of Vigna angularis. The putativeprotein encoded by this cDNA resembled the 1-aminocyclopropane-l-carbox-ylateoxidases (ACC oxidases) identified in other plant species (about80% homology at the amino acid level). Thus, the correspondinggene was designated AB-ACO1 (azuki bean ACC oxidase). GA₃ alsodecreased the activity of ACC oxidase in azuki bean epicotyls,but it did not decrease the rate of ethylene evolution. In fact,GA₃ increased the rate of ethylene evolution and the level ofACC. Thus, GA₃ seemed to increase the production of ethyleneby promoting the synthesis of ACC. (Received January 10, 1997; Accepted July 31, 1997)     

Isolation of a Tobacco cDNA Encoding Sar1 GTPase and Analysis of Its Dominant Mutations in Vesicular Traffic Using a Yeast Complementation System

The cDNA clone of NtSARl, a gene encoding the small GTPase Sar1pwhich is essential for vesicle formation from the endoplasmicreticulum (ER) membrane in yeast, has been isolated from Nicotianatabacum BY-2 cells. NtSAR1 as well as AtSAR1 cDNA isolated fromArabidopsis thaliana [d'Enfert et al. (1992) EMBO J. 11: 4205]could complement the lethality of the disruption of SARI inyeast cells in a temperature-sensitive fashion. They also suppressedyeast sec12 and sec16 temperature-sensitive mutations as yeastSARI does. Using this complementation system, we analyzed thephenotypes of several mutations in plant SAR1 cDNAs in yeastcells. The expression of NtSAR1 H74L and AtSAR1 N129I showeddominant negative effect in growth over the wild-type SARI,which was accompanied by the arrest of ER-to-Golgi transport.Such dominant mutations will be useful to analyze the role ofmembrane trafficking in plant cells, if their expression canbe regulated conditionally. (Received October 29, 1997; Accepted March 17, 1998)     

Cloning and Characterization of High-CO2-Specific cDNAs from a Marine Microalga, Chlorococcum littorale, and Effect of CO2 Concentration and Iron Deficiency on the Gene Expression

Two cDNA clones exclusively induced under an extremely high-CO₂concentration (20%) were isolated from Chlorococcum littoraleby differential screening and named HCR (high-CO₂ response)1 and 2, respectively. The amino acid sequence of the proteinencoded by HCR2 exhibited homology to the gp91-phox protein,a critical component of a human phagocyte oxidoreductase, andto the yeast ferric reductases, Saccharomyces cerevisiae FRE1and FRE2 and Schizosaccharomyces pombe Frpl. The induction ofboth HCR mRNAs required extremely high-CO₂ conditions and irondeficiency, being suppressed under air conditions and by ironsufficiency, suggesting that the expression of these two HCRgenes required extremely high-CO₂ conditions and iron deficiencyin combination. The HCR2 protein was detected in the membranefractions of cells grown under conditions which would favorthe induction of HCR2-mRNA and the protein level was loweredwhen the cells were transferred from iron deficient to 10 µMFeSO₄ conditions (with 20% CO²). (Received September 10, 1997; Accepted November 14, 1997)