Particles Associated with the Outer Epidermal Wall in Internodes of Deepwater Rice

Partial submergence induces rapid internodal growth in deepwaterrice (Oryza saliva L., cv. Habiganj Aman II). The infrastructureof the cell wall/plasmalemma interface of air-grown and submergedinternodes was investigated in the region where cell elongationtakes place. In submerged internodes, electron-dense particlesof about 100 nm diameter were found. These particles were detectableonly at the thick outer wall of the outer epidermis but notat the inner walls. In air-grown control plants, no such granuleswere visible. We suggest that these particles are related tothe process of cell wall growth. The wall weight per unit lengthwas 75% lower in the submerged internode as compared to thatof the air-grown control. This indicates that secondary wallformation is suppressed during submergence of the plant Oryza saliva, deepwater rice, intemodal growth, electron-dense particles     

Characterization of Growth-related Osmiophilic Particles in Corn Coleoptiles and Deepwater Rice Internodes

Osmiophilic particles are secreted from the epidermal cellsinto the outer epidermal cell wall of deepwater rice internodesand corn coleoptiles that have been induced to elongate rapidlyby treatment with gibberellin or auxin, respectively. The diameterof the osmiophilic particles is 80 to 100 nm in deepwater riceand up to 300 nm in corn coleoptiles. Because these particlesare secreted to the outer epidermal wall only, they may containeither cell wall components that are specific for the outerepidermal wall or components of the cuticle that coats the outerepidermal wall. Monensin inhibited the appearance of these particles,indicating that they are derived from the Golgi apparatus. Anattempt was made to identify the contents of the osmiophilicparticles by enzyme-gold or antibody-gold labelling. Cutinase-goldaccumulated mostly in the region of the cell wall just belowthe cuticle. The osmiophilic particles became densely labelledafter incubation with proteinase K-gold, indicating that theyare, at least in part, proteinaceous. In excised tissue andultrathin sections treated with proteinase K, the number ofosmiophilic particles was reduced, while glucanase and cutinasetreatments were without effect. Antibodies against lipid transferprotein, an extensin-like protein, an arabinogalactan protein,a peroxidase, and expansin bound to the cell wall or plasmamembrane but not to the osmiophilic particles.Copyright 1994,1999 Academic Press Epidermal cell wall, gibberellin, indoleacetic acid, osmiophilic particles, Oryza sativa, Zea mays     

Levels of {beta}-Glucan and Lignin in Elongating Internodes of Deepwater Rice

Partial submergence or treatment with either ethylene or gibberellicacid (GA₃ induces rapid growth in deepwater rice (Oryza sativaL.). We correlated the synthesis of two cell wall componentswith two phases of internodal elongation, namely (13,14)-ß-glucanformation with cell elongation and lignification with differentiationof the secondary cell wall and cessation of growth. The contentof ß-glucan was highest in the zone of cell elongationin internodes of air-grown plants and plants that were inducedto grow rapidly by submergence. In the intercalary meristemand in the differentiation zone of the internode, ß-glucanlevels were ca. 70% lower than in the zone of cell elongation.The outer cell layers, enriched in epidermis, contained moreß-glucan in submerged, rapidly growing internodesthan in air-grown, control internodes. The ß-glucancontent of the inner, parenchymal tissue was unaffected or slightlylowered by submergence. The epidermis appears to be the growth-limitingstructure of rapidly growing rice internodes. We hypothesizethat elevated levels of ß-glucan contribute to elongationgrowth by increasing the extensibility of the cell wall. Lignificationwas monitored by measuring the content of lignin and the activitiesof two enzymes of the lignin biosynthetic pathway, coniferylalcohol dehydrogenase (CAD) and phenylalanine ammonia-lyase(PAL), in growing and non-growing regions of the internode.Using submerged whole plants and GA₃-treated excised stem segments,we showed that lignin content and CAD activity were up to sixfoldlower in newly formed internodal tissue of rapidly growing ricethan in slowly growing tissue. No differences were observedin parts of the internode that had been formed prior to inductionof growth. PAL activity was reduced throughout the internodeof submerged plants. We conclude that lignification is one ofthe processes that is suppressed to permit rapid growth. ¹ This work was supported by the National Science Foundationthrough grants No. DCB-8718873 and DCB-9103747 and by the Departmentof Energy through grant No. DE-FGO2-90ER20021. M.S. was therecipient of a fellowship from the Max Kade Foundation.     

Use of Arabidopsis eceriferum Mutants to Explore Plant Cuticle Biosynthesis

The plant cuticle is a waxy outer covering on plants that has a primary role in water conservation, but is also an important barrier against the entry of pathogenic microorganisms. The cuticle is made up of a tough crosslinked polymer called "cutin" and a protective wax layer that seals the plant surface. The waxy layer of the cuticle is obvious on many plants, appearing as a shiny film on the ivy leaf or as a dusty outer covering on the surface of a grape or a cabbage leaf thanks to light scattering crystals present in the wax. Because the cuticle is an essential adaptation of plants to a terrestrial environment, understanding the genes involved in plant cuticle formation has applications in both agriculture and forestry. Today, we''ll show the analysis of plant cuticle mutants identified by forward and reverse genetics approaches. Download video file.^{(163M, mov)}     

Identification of Differentially Expressed Sequence Tags in Rapidly Elongating Phyllostachys pubescens Internodes by Suppressive Subtractive Hybridization

Bamboo shoots grow quickly through the rapid elongation of internodes, but the precise molecular mechanisms underlying this process remain unknown. We used a combination of suppressive subtractive hybridization (SSH), dot blotting, sequencing and bioinformatics to identify Phyllostachys pubescens genes that are differentially expressed in rapidly elongating vs. static internodes (SIs). We isolated 1020 expressed sequence tags (ESTs) by SSH, 173 of which were shown to be differentially expressed by dot blotting. We then sequenced the 20 ESTs showing the greatest difference in expression, 13 of which were preferentially expressed in elongating internodes and seven in SIs. Functional characterization of the ESTs showed that rapid internode elongation requires meristem initiation and proliferation, high-level protein synthesis, cellular respiration, and cell wall synthesis, as well as the regulation of the activated methyl cycle, gibberellin and brassinosteroid biosynthesis, and their signal transduction pathways.     

Expansins and Internodal Growth of Deepwater Rice

The distribution and activity of the cell wall-loosening protein expansin is correlated with internodal growth in deepwater rice (Oryza sativa L.). Acid-induced extension of native cell walls and reconstituted extension of boiled cell walls were confined to the growing region of the internode, i.e. to the intercalary meristem (IM) and the elongation zone. Immunolocalization by tissue printing and immunoblot analysis, using antibody against cucumber expansin 29 as a probe, confirmed that rice expansin occurred primarily in the IM and elongation zone. Rice expansin was localized mainly around the vascular bundles at the base of the IM and along the inner epidermal cell layer surrounding the internodal cavity. Submergence greatly promoted the growth of rice internodes, and cell walls of submerged internodes extended much more in response to acidification than did the cell walls of air-grown internodes. Susceptibility of cell walls to added expansin was also increased in submerged internodes, and analysis by immunoblotting showed that cell walls of submerged internodes contained more expansin than did cell walls of air-grown internodes. Based on these data, we propose that expansin is involved in mediating rapid internodal elongation in submerged deepwater rice internodes.     

深水稻节间伸长生长的机制

淹水可促进深水稻节间快速伸长生长,其主要受内源赤霉素、乙烯、脱落酸等激素信号分子的调控。淹水能促进深水稻植株体内乙烯、赤霉素的生物合成、抑制脱落酸的生物合成,外源乙烯、赤霉素会加速深水稻节间伸长,而外源脱落酸抑制淹水节间的伸长,其中赤霉素是直接作用因子,乙烯能降低内源脱落酸水平、增加节间对赤霉素的敏感性;还与渗透调节、细胞壁组份如膨胀素等有关,淹水及赤霉素都大大增加了膨胀素基因的表达。并就深水稻的进一步研究进行了展望。     

深水稻节间伸长生长的机制

淹水可促进深水稻节间快速伸长生长,其主要受内源赤霉素、乙烯、脱落酸等激素信号分子的调控。淹水能促进深水稻植物株体内乙烯、赤霉素的生物合成、抑制脱落酸的生物合成,外源乙烯、赤霉素会加速深水稻节间伸长,而外源脱落酸抑制淹水节间的伸长,其中赤霉素是直接作用因子,乙烯能降低内源脱落酸水平、增加节地赤霉素的敏感性;还与渗透调节、细胞壁组份如膨胀素等有关,淹水及赤霉素都大大增加了膨胀素基因的表达。并就深水稻的     

Biosynthesis of Ferredoxin-Nitrite Reductase in Rice Seedlings

Changes in ferredoxin-nitrite reductase [EC 1.7.7.1 [EC] ] in etiolatedrice seedlings were followed during induction by nitrate andlight. Etiolated seedlings showed maximal induction of the enzymeactivity during greening with nitrate, while the enzyme activityin etiolated seedlings receiving nitrate in darkness increasedhalf as much as that in nitrate-treated greening plants. Theincrease in nitrite reductase activity during induction coincidedwith an increase in the content of proteins immunoprecipitatedby antibodies raised against spinach nitrite reductase. Lighthad no effect on the induction of the extractable nitrite reductasein the absence of nitrate. Poly(A)⁺-RNA extracted from nitrate-treatedgreening shoots directed the synthesis in a rabbit reticulocyte-lysateof polypeptides immunoprecipitated by spinach nitrite reductaseantibodies. One major polypeptide larger than the native enzymewas found among the translation products, suggesting that nitritereductases in greening rice shoots are synthesized as an precursorform. Analysis of two-dimensional electrophoretograms indicatedthe existence of isoforms of nitrite reductase in rice seedlingswhich had been immunoprecipitated with spinach nitrite reductaseantibodies. ¹To whom all correspondence should be sent. (Received May 15, 1987; Accepted September 7, 1987)     

Regulatory Mechanisms in Anthocyanin Biosynthesis in First Internodes of Sorghum vulgare: Effect of Presumed Inhibitors of Protein Synthesis

There was a 6 to 24-hour lag in the production of anthocyanins in the light after excision of 4-day-old etiolated internodes of Sorghum vulgare variety Wheatland milo. In internodes infiltrated with water, apigeninidin was formed first at 12 to 24 hours and continued to be produced slowly. Luteolinidin was formed slightly later, but its formation rapidly exceeded that of apigeninidin. Cyanidin was the last type to be produced, but equaled the amounts of luteolinidin by 4 days. In noninfiltrated internodes, the production of cyanidin was greatly accelerated, beginning at about 6 hours.     

水稻基部伸长节间性状与茎秆机械强度的相关分析和QTL定位

分析水稻品种‘沈农265’和‘丽江新团黑谷’杂交的F2群体基部第二节间茎秆机械强度与该节间形态和茎秆解剖结构的相关性,并对基部第二节间机械强度和相关性状进行QTL定位的结果表明：机械强度与茎粗、茎壁面积、茎壁厚度、大小维管束数目、大小维管束面积、大小维管束韧皮部面积、大小维管束木质部面积呈显著或极显著的正相关,与节间长度呈极显著的负相关,而与茎秆扁平率的相关不显著。采用复合区间作图,从研究的14个目标性状中检测到18个QTL。控制基部第二节间的抗折力的QTL检测到4个,位于第4、7、9和10号染色体上,可解释遗传变异的12%～23%。在第4和第7染色体上的相同区间上还同时检测到了控制茎壁性状和维管束性状QTL,贡献率在12%～21%之间。说明这两个位点是控制基部第二节间机械强度的重要区域,也是茎壁性状、维管束性状与机械强度高度正相关的遗传学基础。     

Contrasts in the Nitrogenous Composition of Rapidly Growing and Non-growing Plant Tissues1

Contrasts have been drawn between the nitrogenous compositionof rapidly proliferating tissue and that of the resting, non-growingtissues from which it was derived. The alcohol soluble fractionand the hydrolysate of the alcohol-insoluble fraction of tissuein these contrasted states have been examined by the methodsof quantitative partition chromatography. The ratio of alcohol-soluble to alcohol-insoluble nitrogen wasmuch greater in the resting than in the proliferating tissue.These differences were due mainly to a very much lower contentof amino-acids and amides in the growing tissue, especiallyof asparagine, glutamine, and arginine. Only -aminobutyric acidincreased in its content in the growing potato cells. Without regard to the means adopted to induce growth the protein-nitrogenof the dividing cells was conspicuously rich in hydroxy-L-proline,an amino acid, which is conspicuous in collagen but not normallyso in plant proteins. The proteins of the growing cells alsotend to be rich in the basic amino-acids. It is suggested that the hydroxyproline-rich protein moietyis a characteristic feature of the proliferating cells and itspossible significance is noted.     

Physicochemical Characterization of Tween 80-Hydrolyzing Esterases Produced by Rapidly Growing Mycobacteria

Tween 80-hydrolyzing esterases produced by various species of rapidly growing mycobacteria were partially purified from sonicated cell lysates by diethylaminoethyl (DEAE) cellulose and subsequent Sephadex G-150 column chromatographies. The amount of the esterase produced per gram of bacterial cells varied markedly with each species. Mycobacterium smegmatis, M. chelonei, and M. phlei were high producers and M. chitae and M. diernhoferi were low producers of Tween-hydrolyzing esterase. The resistance of each mycobacterial strain to oleic acid correlated well with their esterase-producing ability. All the esterases studied were adsorbed on DEAE cellulose in 50 mM Tris-HCl buffer (pH 7.5), indicating that they are acidic proteins. Esterases of M. smegmatis, M. chitae, M. fortuitum, and M. phlei were eluted from DEAE at high concentrations (0.11–0.18 m) of ammonium sulfate, while those of M. parafortuitum and M. diernhoferi were eluted at lower concentrations (0.05–0.08 m). With Sephadex G-150 gel filtration, all esterases were shown to have similar molecular weights (36,000 to 58,000). On the basis of heat-stability and trypsin- or chymotrypsin-sensitivity, these esterases were divided into three groups: one was heat-stable and protease-sensitive (M. smegmatis and M. fotuitum), another was heat-labile and protease-resistant (M. chelonei), and the other was the intermediate of the above two groups (M. diernhoferi).     

长穗颈温敏核不育水稻穗颈节间伸长与内源激素的关系

以水稻品种'长选3S'为研究对象,以'培矮64S'为对照,检测幼穗不同发育时期水稻穗颈节间中GA1、IAA、Z、ZR和ABA含量变化的结果表明,从二核期至始花后第3天,'长选3S'穗颈节间中的GA1和IAA含量先升后降,三核期出现峰值,'长选3S'穗颈节间中的GA1和IAA含量分别比'培矮64S'高6.5～10.6倍和9.5～26.9倍.在二核期和三核期,'长选3S'穗颈节间中GA1/ABA和IAA/ABA比值比'培矮64S'高,其(Z ZR)/ABA比值稍高,而Z ZR和ABA含量均比其低.这些结果表明水稻长穗颈基因还可能是通过调节激素之间平衡而控制水稻的茎伸长生长的.     

温敏核不育水稻穗颈节间的SSH特异表达

‘长选3S’是由‘培矮64S’通过辐射诱变选育出的长穗颈温敏核不育水稻．以‘K选3s’二核花粉期穗颈节问作为目标群体,‘培矮64S’二核花粉期穗颈节间作为对照群体,进行抑制差减杂交,川经过‘培矮64S’cDNA差减的‘长选3S’cDNA构建了一个含有大约130个独立克隆的差减文库;采用差减前的‘培矮64S’cDNA和‘长选3S’cDNA以及正向／反向差减杂交后的cDNA为模板标记探针,对随机挑取的96个承组质粒进行羞示筛选,获得了20个阳性候选克隆。从这些阳性候选克隆中随机挑取了8个进行Northern blot分析．证实其巾中1个候选克隆代表了在‘长选3S’穗颈节间中特异表达的基因．序列分析和同源性比较表明它与信号传导有关。这一在‘长选3S’穗颈节间特异表达的cDNA片段有助于进一步揭示其穗颈节间伸长的分子机制．并为水稻不育系的遗传改良提供有用的素材。     

Molecular Events Underlying Coordinated Hormone Action in Submergence Escape Response of Deepwater Rice

Recent studies revealed that some rice varieties adopt opposite strategies to overcome flooding stress. While certain varieties hold metabolism and stay stunted until floodwater recedes, deepwater rice varieties undergo rapid stem elongation and do not suffer drowning problems. Both varieties use the same signaling agents, the ethylene response factors, as key factors even though they display opposite submergence responses. In deepwater rice, ethylene response factor genes SNORKEL1 and SNORKEL2 are believed to play a major role in submergence escape by mediating ethylene signaling, which leads to rapid stem elongation. These genes connect hormone signaling cascades from ethylene to ABA and gibberellins (GAs). Submergence increases ethylene levels in the internodal space, ethylene upregulates an ABA inactivating enzyme gene, OsCYP707A5 or OsABA8ox1, and some GA metabolism genes such as OsGA20ox genes and OsGA3ox genes. As a result of gene regulation by ethylene, internodal ABA levels decrease while GA levels increase, finally upregulating growth-related genes like expansin genes (OsEXPs). Along with the ethylene signaling in submergence, it is necessary to consider an alternative signaling pathway induced by hypoxia. Taken together, study on the submergence responses of rice plants will lead to improvement of crop production and contribution to basic research on plant growth.     

Exudates from Rice Callus Tissues Resulting from the Lack of Cuticle and Wax Layers

Nondialyzable melanoidins prepared from a glucose-glycine system were investigated as to their decolorization and degradation products on ozone treatment. Melanoidins were decolorized to degrees of 84 and 97% after ozonolysis at — 1°C for lOmin and 90min, respectively, and the mean molecular weight of melanoidins decreased from 7000 to 3000 after ozonolysis for 40 min. The major components of electrofocused melanoidins before and after ozone treatment had pis of 3.00 and 2.86, respectively, the pI 3.00 band being significantly affected.

IR measurement showed that the absorption at 1290 cm^?1 disappeared and that at 1720 cm^?1 newly appeared on ozonolysis, respectively, and the absorption at 1620 cm^?1 disappeared on acid hydrolysis after ozonolysis.

Furthermore, the major degradation products in the ether-soluble fractions obtained from ozone-treated melanoidins were identified as butanedioic acid, glycolic acid, 2-hydroxybutanoic acid and so on.

In the aqueous fraction, one of the major products was glycine, which was produced to the level of 1.05% on ozonolysis which increased to 5.75% per melanoidin on acid hydrolysis after ozonolysis. From these findings and the IR results, it is postulated that glycine was considerably incorporated into melanoidin molecules as the amide form.