Modification of Leaf Size in Rice (Oryza sativa L.) and its Effects on Water Stress-induced Abscisic Acid Accumulation

The ability of detached leaves of the rice cultivars IR20 and63–83 and their F₂ progeny to accumulate ABA in responseto water stress is negatively correlated with leaf size. Itwas shown that this association was not an artifact of incubationconditions following the imposition of stress. Also, it waspossible to break the correlation by selecting plants in segregatingpopulations which differed in ABA yet had similar leaf size. In further experiments, leaf size was altered phenotypicallyby various treatments; either being increased by gibberellinapplication or periodic removal of tillers, or reduced by priorexposure to water stress or ABA. Although responses to thesetreatments were complex, the results demonstrated that leafsize and accumulation capacity were at least partially independent.It is suggested that the correlations observed previously inF₂ populations from the cross IR20 x 63–83 were a resultof genetic linkage. Oryza saliva L., rice, leaf size, abscisic acid, water stress     

Abscisic Acid and Water Relations of Rice (Oryza sativa L.): Effects of Drought Conditioning on Abscisic Acid Accumulation in the Leaf and Stomatal Response

The effects of a period of water stress (drought conditioning)on responses to a second (challenge) stress were examined inyoung vegetative rice (Oryza sativa L.) plants. Drought conditioningdid not affect the rate of subsequent stress development, nor,in a first experiment, did it influence relations between turgor(_p) and total () leaf water potential. However, conditioningdid extend the range of _p over which stomata remained open andsignificantly reduced the amount of ABA which accumulated inthe leaf at a given _p. The change in stomatal behaviour (stomataladjustment) was quantitatively accounted for by the change inleaf ABA accumulation. The reduction in ABA accumulation due to conditioning did notinvolve a change in the potential capacity to produce ABA, asABA accumulation in partially dehydrated detached leaves wasnot reduced by conditioning. It is suggested that effects ofconditioning on leaf ABA content in the intact plant involvechanges in the rate of ABA export from the leaf. Oryza sativa L, rice, drought conditioning, stomata, water stress, abscisic acid     

Effects of Atmospheric Humidity on Abscisic Acid Accumulation and Water Status in Leaves of Rice (Oryza sativa L.)

Rice (Oryza sativa L ) plants were grown in controlled environmentcabinets with either low (c 0 4 kPa) or high (c 1 6 kPa) atmosphericwater vapour pressure deficit (v p d) The capacity of detachedleaves to accumulate ABA in response to rapidly induced waterstress was increased when plants were grown at high v p d Highv p d significantly lowered solute potential (     

Effects of Abscisic Acid and Water Stress on the Senescence of Detached Rice Leaves

The effects of abscisic acid (ABA) and water stress on senescence and enzyme activities of oxygen scavenging enzymes of detached rice leaves were compared. Exogenously applied ABA exhibited water stress-like effects by promoting senescence, by decreasing the activities of catalase, peroxidase, ascorbate peroxidase and superoxide dismutase. It seems that the effects of water stress on senescence and enzyme activities are possibly mediated through increased content of endogenous ABA. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Relation between Accumulation of Abscisic Acid and Proline in Detached Rice Leaves

The relation between abscisic acid (ABA) and proline accumulation was investigated in detached rice (Oryza sativa L.) leaves. In darkness, proline content increased about 2-, 2,5- and 6-fold after 24, 48 and 72 h. ABA content reached maximum after 48 h. In the light, proline content remained almost unchanged until 48 h and subsequently increased slightly. ABA content in the light was lower than in darkness, but the maximum was also after 48 h. During 12-h exposure to decreased air humidity, proline content gradually increased, but ABA content increased about 25-fold after 4 h and declined thereafter. Exogenous application of ABA resulted in an increase in proline content in detached rice leaves under both light and darkness.     

Ethylene-Induced Polyamine Accumulation in Rice (Oryza sativa L.) Coleoptiles

The light-harvesting complex (LHC) of photosystem II is composed of several different pigment-binding apoproteins. We have identified a cDNA clone LHCIIa-1 encoding the 31-kilodalton LHC IIa (CP29, Chl a/b-P1) apoprotein of barley (Hordeum vulgare). Direct protein microsequencing of an internal peptide fragment from the LHC IIa apoprotein has been used to identify unequivocally the cDNA clone as that coding for the LHC IIa apoprotein. Microsequencing of the 28-kilodalton LHC IIc protein (CP26) showed only minor sequence similarity to the LHC IIa protein, indicating that they are two different gene products. LHCIIa-1 codes for a protein of 286 amino acid residues (molecular weight, 31,308), which displays strong similarities to other pigment-binding LHC proteins, and yet contains an additional 42 amino acid residue segment. Two regions of strong intramolecular sequence similarity are also observed.     

Ethylene-Induced Inhibition of Root Growth Requires Abscisic Acid Function in Rice (Oryza sativa L.) Seedlings

Ethylene and abscisic acid (ABA) have a complicated interplay in many developmental processes. Their interaction in rice is largely unclear. Here, we characterized a rice ethylene-response mutant mhz4, which exhibited reduced ethylene-response in roots but enhanced ethylene-response in coleoptiles of etiolated seedlings. MHZ4 was identified through map-based cloning and encoded a chloroplast-localized membrane protein homologous to Arabidopsis thaliana (Arabidopsis) ABA4, which is responsible for a branch of ABA biosynthesis. MHZ4 mutation reduced ABA level, but promoted ethylene production. Ethylene induced MHZ4 expression and promoted ABA accumulation in roots. MHZ4 overexpression resulted in enhanced and reduced ethylene response in roots and coleoptiles, respectively. In root, MHZ4-dependent ABA pathway acts at or downstream of ethylene receptors and positively regulates root ethylene response. This ethylene-ABA interaction mode is different from that reported in Arabidopsis, where ethylene-mediated root inhibition is independent of ABA function. In coleoptile, MHZ4-dependent ABA pathway acts at or upstream of OsEIN2 to negatively regulate coleoptile ethylene response, possibly by affecting OsEIN2 expression. At mature stage, mhz4 mutation affects branching and adventitious root formation on stem nodes of higher positions, as well as yield-related traits. Together, our findings reveal a novel mode of interplay between ethylene and ABA in control of rice growth and development.     

栽培稻旱胁迫叶片相关性状的遗传解析

利用籼稻窄叶青8号(ZYQ8)和粳稻京系17(JX17)衍生的加倍单倍体(DH)群体127个株系,2002年在杭州采用田间断水法栽培,在水分胁迫下,对叶片的卷叶、相对含水量和电导率3个性状进行了评价和QTL分析。结果表明,3个性状在DH群体中均存在双向超亲分离,接近正态分布,受数量性状基因的控制;检测到影响这些性状的6个QTL,其中卷叶3个(qLR—1,qLR—5和qLR—11)、相对含水量2个(qRWC—1和qRWC—6和电导率1个(qERC—6）。旱胁迫时,目测卷叶方便易行,适于对大批品种或资源筛选,对抗旱栽培稻品种的筛选和利用具有一定的指导意义。     

Coleoptile Senescence in Rice (Oryza sativa L.)

We investigated the cellular events associated with cell deathin the coleoptile of rice plants (Oryza sativa L.). Seeds germinatedunder submergence produced coleoptiles that were more elongatedthan those grown under aerobic conditions. Transfer of seedlingsto aerobic conditions was associated with coleoptile opening(i.e. splitting) due to death of specific cells in the sideof the organ. Another type of cell death occurred in the formationof lysigenous aerenchyma. Senescence of the coleoptile was alsonoted, during which discolouration of the chlorophyll and tissuebrowning were apparent. DNA fragmentation was observed by deoxynucleotidyltransferase-mediateddUTP nick end labelling (TUNEL) assay, and further confirmedby the appearance of oligonucleosomal DNA ladders in senescentcoleoptile cells. Two nucleases (Nuc-a and Nuc-b) were detectedby in-gel-assay from proteins isolated from coleoptiles. Nuc-a,commonly observed in three cell death phases required eitherCa²⁺or Mg²⁺, whereas Nuc-b which appeared during senescencerequired both Ca²⁺and Mg²⁺. Both nucleases were strongly inhibitedby Zn²⁺. Copyright 2000 Annals of Botany Company Aerenchyma, rice, cell death, coleoptile, fragmentation, nuclease, Oryza sativa, senescence, split, submergence, TUNEL     

水稻体细胞无性系变异

水稻体细胞无性系变异研究取得了很大进展 ,获得了大量抗病、抗逆、优质、矮杆等突变体。对这些突变体遗传分析表明 ,大多数突变性状由 1对或 2对基因控制。水稻体细胞无性系变异的发生与基因型、性状、继代时间、培养方式等有关 ,并具有内在的机制 ,点突变和反转录转座子插入可能是引起水稻无性系变异的两个重要原因。     

Alteration of Leaf Metabolism in Bt-Transgenic Rice (Oryza sativa L.) and Its Wild Type under Insecticide Stress

Insecticide is always used to control the damage from pests, while the potential influence on plants is rarely known. Time-course metabolic changes of wild and Bacillus thuringiensis (Bt) transgenic rice (Oryza sativa L.) plants after insecticide treatment were investigated by using gas chromatography-mass spectrometry (GC-MS). A combined statistical strategy of 2-way ANOVA and multivariate analyses (principal component analysis and hierarchal cluster analysis) was performed to find the stress-associated effects. The results reveal that a wide range of metabolites were dynamically varied in both varieties as a response to insecticide, in multiple metabolic pathways, such as biosynthesis and metabolism of amino acids, carbohydrates, fatty acids, TCA cycle, and the shikimate/phenylpropanoid pathway, and most of the changes were correlated with the exposure time and dependent on the variety. A set of stress defenses were activated, including phytohormone signaling pathway, antioxidant defense system, shikimate-mediated secondary metabolism, and so on. In particular, insecticide led to much stronger regulations of signaling molecules (salicylate and the precursor of jasmonate) and antioxidants (α-tocopherol and dehydroascorbate/ascorbate) in Bt-transgenic variety at the early stage. Our results demonstrated that the Bt-transgenic rice had a more acute and drastic response to insecticide stress than its non-transgenic counterpart in antioxidant system and signaling regulation.     

Characteristics of the Induction of the Accumulation of Proline by Abscisic Acid and Isobutyric Acid in Detached Rice Leaves

The effects of abscisic acid and isobutyric acid on levels ofproline in detached rice leaves were compared. The lowest concentrationof abscisic acid that induces accumulation of proline in detachedrice leaves was much lower than that of isobutyric acid. Theaccumulation of porline induced by isobutyric acid was associatedwith acidification of the cell sap, whereas abscisic acid increasedlevels of proline without decreasing the pH of the cell sap.Potassium chloride enhanced the accumulation of proline thatwas induced by abscisic acid, but it did not stimulate thatinduced by isobutyric acid. Of particular interest is the findingthat detached rice leaves treated with fusicoccin showed anincrease in levels of proline and a decrease in the pH of thecell sap. A synergistic increase in levels of proline was observedwhen fusicoccin and abscisic acid applied simultaneously. However,fusicoccin had no effect on the induction of the accumulationof pro-line by isobutyric acid. Benzyladenine inhibited theinduction by abscisic acid of the accumulation of proline, butit did not inhibit the induction by isobutyric acid. It is concludedthat the mode of action of abscisic acid in inducing the accumulationof proline differs from that of isobutyric acid. Our resultsalso indicate that factors other than acidification of the cellsap are involved in regulation of the accumulation of proline. (Received September 25, 1990; Accepted December 20, 1990)     

Release of Nitrogen From Chloroplasts During Leaf Senescence in Rice (Oryza sativa L.)

In order to ascertain the possibility that nitrogen associatedwith chloroplasts serves as a major source of nitrogen redistributedfrom senescent leaves, chloroplasts were isolated from riceleaves and changes with leaf age in total leaf nitrogen andchloroplast nitrogen were examined. Results presented here showthat decrease in total leaf nitrogen during leaf senescencewas closely correlated with decrease of chloroplast nitrogenand roughly 85–95 per cent of leaf nitrogen released fromsenescent leaves during the experimental period could be accountedfor by a loss of chloroplast nitrogen. By dividing chloroplastnitrogen into two fractions, i.e. lamellar and stroma fractions,the question of which fraction was more deeply concerned withthe loss of leaf nitrogen was clarified. Results suggested thatin the vegetative stage of plant growth the stroma was mainlyresponsible for the loss of leaf nitrogen. On the other hand,nitrogen was released from lamellar and stromal fractions atalmost the same rate during the reproductive stage. Oryza sativa L., rice, chloroplasts, nitrogen, leaf senescence     

水稻对叶瘟和穗瘟部分抗性的遗传分析

在一个水稻籼籼交重组自交系群体中,选用由感病株系构成的2个亚群体和2个不同的稻瘟病菌小种,进行了水稻对叶瘟部分抗性的QTL定位,还选用由感病而且抽穗期相近的株系构成的亚群体和另一个病菌小种,进行了水稻对穗瘟部分抗性的QTL定位,将病叶面积百分比(DLA)、病斑大小(LS)和病斑数(LN)作为对叶瘟部分抗性的性状,将病斑长度(LL)和孢子量(CA)作为对穗瘟部分抗性的性状。所构建的图谱包含168个标记。应用QTLMapper 1．01b,共检测到11个表现主效应的QTL和28对双因子互作,有3个表现主效应的QTL参与对同一性状的互作。QTL的主效应对单一性状的贡献率为4．7％～38．8％,而上位性效应对单一性状的贡献率为16．0％～51．7％,QTL的主效应对大多数性状的贡献率小于互作效应,表明互作效应对于部分抗性的重要作用。对穗瘟部分抗性的两个性状LL和CA,所检测到QTL总效应的贡献率分别达到70．6％和82．6％,表明由排除了主效抗病基因的感病株系组成的亚群体适合于进行部分抗性QTL定位。     

Proteomic Analysis of Upland Rice (Oryza sativa L.) Exposed to Intermittent Water Deficit

Rice is the most important crop consumed all over the world. In Brazil, irrigated rice covers 50 % of the rice producing area and is responsible for 75 % of the national production. Upland rice covers most of the remaining area, and is therefore, a very important production system in the country. In the present study, we have used the drought tolerant upland rice variety Três Meses Antigo to investigate the proteomic changes that occur during drought stress. Plants were submitted to drought by the reposition of 50 % of the water lost daily. Twenty days after the beginning of the drought stress period, leaves were harvested and used for protein extraction. The 2D maps obtained from treated and control plants revealed 408 reproducible spots, 44 of which were identified by mass spectrometry, including 15 differential proteins. Several unaltered proteins were also identified (39 spots) and were mainly involved in photosynthesis. Taken together, the results obtained suggest that the tolerant upland rice up-regulates anti-oxidant and energy production related proteins in order to cope with water deficit.     

NaCl-induced Senescence in Leaves of Rice (Oryza sativa L.) Cultivars Differing in Salinity Resistance

The influence of NaCl on senescence-related parameters (proteinand chlorophyll concentrations, membrane permeability and chlorophyllfluorescence) was investigated in young and old leaves of fiverice cultivars differing in salt resistance. NaCl hastened thenaturally-occurring senescence of rice leaves which normallyappears during leaf ontogeny: it decreased chlorophyll and proteinconcentrations and increased membrane permeability and malondialdehydesynthesis. Such an acceleration of deteriorative processes affectedall leaves in salt-sensitive cultivars while it was more markedin oldest than in youngest leaves of salt-resistant genotypes.NaCl-induced senescence also involved specific modifications,such as an increase in basal non-variable chlorophyll fluorescence(F ₀) recorded in all cultivars or a transient increase in solubleprotein concentration recorded in salt-resistant genotypes only.Alteration of membrane permeability appeared as one of the firstsymptoms of senescence in rice leaves and allowed discriminationamong cultivars after only 7 d of stress. In contrast, F _v/F _mratio (variable fluorescence/maximal fluorescence) was thesame for all cultivars during the first 18 d of stress and thuscould not be used for identifying salt-resistant rice exposedto normal light conditions. Relationships between parametersinvolved in leaf senescence are discussed in relation to salinityresistance of rice cultivars. Chlorophyll concentration; chlorophyll fluorescence; electrolyte leakage; magnesium; malondialdehyde; membrane permeability; NaCl; Oryza sativa L.; protein; rice; salinity resistance; senescence; UV absorbing substances     

水稻苗期生长对缺磷响应的QTL定位(英文)

缺磷是抑制全球水稻产量主要因素之一。本研究利用Asomonori(粳型)/IR24(籼型)杂交重组自交株系,对5个水稻苗期性状(相对苗高、相对根长、相对根重、相对苗重以及相对总重)在缺磷条件下的响应QTL进行定位。共检测到20个水稻苗期生长对缺磷响应的QTL位点,分别位于第1(4QTLs)、第4(4QTLs)、第5(2QTLs)、第7、第8(4QTLs)、第9(2QTLs)、第11(2QTLs)和第12号染色体上,其中13个QTLs位于与C3029C、XNpb302、C621B、C621C、R2976和C1263分子标记紧密连锁的6个基因组区域上。另外,每个性状均能从双亲中检测到正负效应QTL位点,这些能解释重组自交系群体中出现超亲和连续分布的现象。本文主要报道了水稻第5、第7和第11染色体上存在水稻苗期生长对缺磷响应的QTL位点。研究表明,该结果及其中检测到的QTLs两侧的连锁分子标记可用于水稻苗期耐低磷性分子育种。     

The Remobilization of Nitrogen Related to Leaf Growth and Senescence in Rice Plants (Oryza sativa L.)

Rice plants (Oryzae sativa L.) grown in a nutrient solutionwere fed with (¹⁵NH₄)₂SO₄ during the 5 days of their young panicleformation. At the end of that time in the youngest leaf blade, which hadstarted to emerge during the labelling, absorbed-nitrogen accountedfor 37% of the increased nitrogen of the tissue; in the nextdeveloping leaf blade it accounted for 55%. Thus, remobilized-nitrogenoriginating from older patrs of the plant made up 63 and 45%,respectively, of their total nitrogen. The important contributionof the remobilized-nitrogen to the development of a leaf isevident. The remobilization of nitrogen in the 12th leaf blade on themain stem was examined in detail after labelling during itsdeveloping stage. The ¹⁵N level started to decrease soon afterthe end of the labelling period and continued to decrease untilfull senescence, although the total nitrogen in the same leafincreased until just after its complete expansion, suggestingthat even a young leaf plays a role as a supplier of remobilized-nitrogen. During the rapid decrease in the total nitrogen after its peakat full expansion of the leaf, the actual proportion of labelledabsorbed nitrogen remained nearly the same, indicating thatinflux of new nitrogen into a senescing leaf is very limited. (Received March 13, 1981; Accepted July 13, 1981)