D-Amino-acid-stimulated ethylene production in seed tissues

Ethylene production by axial and cotyledonary tissues excised from Xanthium pennsylvanicum Wallr. seeds was markedly (up to 5-fold) stimulated by the D-isomers of phenylalanine, valine, leucine, threonine, methionine and eithionine while the L-isomers caused no such effect. Responsiveness of these seed tissues to D-methionine appeared soon after the beginning of imbibition, reached a maximum after 6–12 and 12–24 h for the axial and cotyledonary tissues, respectively, and then decreased sharply. D-Phenylalanine and D-methionine also stimulated ethylene production in seed tissues of X. canadense Mill. and in cotyledonary segments from seeds of Helianthus annuus L., Cucurbita moschata Duch. and Vigna radiata (L.) Wilczek. The endogeneous ethylene production and the D-amino-acid-stimulated ethylene production by the seed segments was strongly inhibited by aminoethoxyvinyl glycine, a potent inhibitor of ethylene synthesis from L-methionine.     

Hormonal regulation of tiller dynamics in differentially-tillering rice cultivars

Tiller number can contribute significantly to yield potential of rice, but little knowledge is available on hormonal regulation of tillering and tiller dynamics. In the present study, Indole-3-acetic acid (IAA), kinetin (6-furfuryl amino purine) and Gibberellic acid (GA₃) treatments have been applied at the early tillering stage to two rice cultivars that contrast for tiller number. The responses of the hormones were studied on growth, development, grain yield, senescence patterns, assimilate concentration of the panicle and ethylene production in different classes of tillers. The leaf area, panicle grain number, fertility percentage and grain yield of tillers were higher in the low-tillering cultivar than that of high-tillering cultivar; the treatment of kinetin was more effective in the latter than in the former. High ethylene production was responsible for reduction of growth duration and grain yield of the tillers. Kinetin application reduced ethylene production of the late-tillers significantly for the benefit of grain yield.     

Screening technique for differentiating the degree of spikelet filling in rice

Summary Fully filled spikelets were determined by specific gravity method in some rice varieties. As specific gravity increased, the filled spikelets decreased while the test weight (1000-grain weight) increased. The potential test weight was found to be more than the weight known for the variety. Different grades of grain were characterised as (i) average (ii) good and (iii) Very good based on the degree of spikelet filling. The fully fitted spikelets were found to be lower in all the varieties tested and the partially filled but useful for yield calculations were higher. The grain grade index denotes the proportion of fully filled spikelets recovered at 1.18 specific gravity to the total number of spikelets formed. It was suggested that this inded is useful as a screening tool in varietal improvement programme for identifying high yield potential plants.     

Ethylene control of seed coat development in low and high sterile semidwarf indica rice cultivars

Although basally positioned inferior spikelets of rice panicles emerge late from the flag leaf enclosure (boot), they mature early which precludes adequate grain filling. It is assumed that extended exposure to ethylene inside the boot restricts assimilate partitioning to the endosperm in basal spikelets by affecting the functions of seed coat. In the present study, ethylene concentration inside the boot was measured in two high yielding rice cultivars differing in percentage of spikelet sterility. To manipulate the concentration/action of ethylene, silver nitrate, aminoethoxyvinyl glycine and 2-chloroethylphosphonic acid were injected into the boot. The effect of these chemicals on the concentration of photosynthetic pigments, lipid peroxidation and peroxidase activity of the seed coat and lemma and palea were measured to monitor development. Ethylene reduced development during the juvenile phase but accelerated degradation of the photosynthetic tissues of the spikelets in the senescent phase. Boot ethylene correlated positively with number of barren spikelets in the panicle and negatively with concentration of photosynthetic pigments of the seed coat of inferior spikelets. The concentration of ethylene was higher in the high sterile cultivar Mahalaxmi than that of the low sterile Mahanadi. Inhibition of ethylene action or synthesis improved grain filling. The chemicals were most effective on the inferior spikelets. It was concluded that ethylene retarded seed coat development during the prestorage phase and reduced grain filling of basal spikelets.     

开放式空气CO2浓度增高对水稻颖花分化和退化的影响

在大田栽培条件下 ,研究开放式空气CO2 浓度增加 (FACE) 2 0 0 μmol·mol-1的处理对水稻每穗 1、2次枝梗及其颖花的分化数、退化数、现存数及退化率的影响 .结果表明 ,FACE处理对每穗 1、2次枝梗的分化数及 1次枝梗的退化数、退化率均无显著影响 ,但使 2次枝梗的退化数、退化率显著提高 ,使 2次枝梗现存数明显减少 ;FACE处理对每穗 1、2次颖花的分化数和 1次颖花的退化数、现存数、退化率均无显著影响 ,但使每穗 2次颖花的退化数和退化率显著提高 ;FACE处理使每穗颖花现存数显著减少主要是因为FACE处理使现存 1次枝梗上 2次枝梗大量退化引起 2次颖花退化所致 ;FACE处理使 1次颖花现存数占全穗的比率显著增加 ,使 2次颖花现存数占全穗的比率显著降低 .     

Characterization of 1-aminocyclopropane-1-carboxylate deaminase producing methylobacteria from phyllosphere of rice and their role in ethylene regulation

The presence of 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity among the phyllosphere methylobacteria of rice was detected and its role in regulating plant ethylene level was assessed. Eighteen methylobacterial isolates from four different cultivars of rice were isolated and screened for ACCD. The 16S rRNA homology of ACCD positive methylobacterial isolate closely related to the species Methylobacterium radiotolerans. The accD gene sequence homology of the isolate was 98% similar to Rhizobium leguminosarum. Foliar spray of ACCD positive methylobacterial isolates enhanced the root and shoot length of rice and tomato seedlings under gnotobiotic condition and lower the ethylene level (60–80%) in the plant species.     

Low levels of oxygen promote internodal elongation in floating rice independently of enhanced ethylene production

Submergence induces rapid elongation of internodes in floating rice(Oryza sativa L. cv. Habiganj Aman II). The initial signalfor such internodal elongation has been considered to be the reduced partialpressure of oxygen in submerged internodal cavities, which promotes theelongation of internodes through the enhancement of ethylene synthesis. Weexamined the relationship between low oxygen pressure and ethylene production inthe rapid elongation of floating rice internodes using ethylene biosynthesisinhibitors, aminooxyacetic acid (AOA) and CoCl₂. When floating ricestem segments were incubated in an atmosphere of low O₂, internodalelongation accelerated and ethylene production increased. However, in stemsegments treated with AOA or CoCl₂, low O₂ stillstimulated the elongation of internodes although the ethylene production by theinternodes was less than by those in control stem segments where internodalelongation was not promoted. These results indicate that low O₂ iscapable of causing rapid elongation of internodes of floating rice independentlyof enhanced production of ethylene. In addition to low O₂,submergence, ethylene and gibberellic acid each enhanced the production ofethylene by internodal tissues, suggesting that enhanced ethylene production isa common phenomenon accompanied by the acceleration of internodal elongation infloating rice.     

Carbon footprints of rice production in five typical rice districts in China

Five provinces located in the five main rice-growing regions in China were selected as study areas, which were Jiangsu, Heilongjiang, Sichuan, Guangdong and Hunan province respectively in the middle and lower reaches of the Yangtze River, northern, southwest, southern and central rice districts. Carbon footprints of rice production in these five provinces were calculated through the life cycle assessment method using governmental statistical data, industrial standards and relevant technical data separately. Material and energy consumptions were estimated, key stages of energy consumptions and carbon emissions were identified as well. Moreover, improving measurements had been suggested correspondingly. The results indicated that: the energy consumptions of rice production in these five provinces ranked as following (high to low): Guangdong, Heilongjiang, Hunan, Sichuan and Jiangsu. The carbon footprints of rice production were 2504.20 kg carbon dioxide equation per ton rice (kgCO₂-eq./t) (Guangdong province), 2326.47 kgCO₂-eq./t (Hunan province), 1889.97 kgCO₂-eq./t (Heilongjiang province), 1538.90 kgCO₂-eq./t (Sichuan province) and 1344.92 kgCO₂-eq./t (Jiangsu province) respectively. Reducing the quantities of urea and using the intermittent irrigation method could decrease energy consumption as well as carbon footprint.     

Dynamic Changes of Endogenous Plant Hormones in Rice Grains in Different Parts of Panicle at Grain filling Stage

The grain fresh weight and grain-filling rate at early grain developing stage in rice ( Oryza sativa L. ) were higher in the upper than in the lower part of panicle during grain filling. The grains in the upper and/or the lower part of panicle were analyzed for the endogenous plant hormones. The results indicated that the peak content of ABA and/or GA1 + 3 in the developing grains appeared at about the same stage when the highest increasing rate of grain appeared in the upper and in the lower part of the panicle respectively. After heading, the IAA content in developing grains steadily decreased in both the upper and the lower part of the panicle, GAn + 7 content decreased at first and then increased, and again decreased. At the early grain-filling stage, the ABA and GA1 + 3 contents in the developing grains were higher in the upper than in the lower part of the panicle. The role that the hormones play in the developing grains and the reason why the grains seed set better in the upper than in the lower part of the panicle were discussed.     

Involvement of ethylene in the morphological and developmental response of rice to elevated atmospheric CO2 concentrations

We tested the hypothesis that increased carbohydrate flux under elevatedCO₂ regulates accelerated development using rice (Oryzasativa L. cv. Jarrah). Plants were grown either in flooded soil orsolution culture at either 360 or 700 L CO₂L^–1. Total dry mass, shoot elongation rates (SER),tiller appearance rates (TAR) and ethylene release from intact rice seedlingswere measured from 5 to 42 days after planting (DAP). At maturity, shoot andsheath length, tiller number and grain mass were also measured. ElevatedCO₂ had a profound effect on growth, morphology and development andthe effects were more pronounced during the early growth phase. Total aboveground biomass increased at elevated CO₂ and this was accounted for by enhanced tiller number. Grain yield was increased by 56% under elevated CO₂mainly due to increased tiller number and hence panicle number. TAR and SERwereenhanced at elevated CO₂ but SER increased only untill 25 DAP.Elevated CO₂ stimulated a 2-3-fold increase in endogenous andACC-mediated ethylene release but the ACC concentration in the leaves waslittleaffected showing that rates of ACC synthesis matched its oxidation. Inhibitionof ethylene action by 1-aminocyclopropane (1-MCP) had a more pronouncedinhibitory effect on ethylene release in plants that were grown at 700 ascompared to 360 L CO₂ L^–1. Feedingsucrose to intact plants enhanced ethylene synthesis and these results areconsistent with the hypothesis that increased accumulation of sucrose atelevated CO₂ may enhance expression of genes in the ethylenebiosynthetic pathway. We conclude that increase in ethylene release may becentral in promoting accelerated development under elevated CO₂ andthis coincides with the release of auxiliary buds and accelerated rates oftiller appearance hence increased grain yield at elevated CO₂.     

Progress of ethylene action mechanism and its application on plant type formation in crops

BackgroundThe plant hormone ethylene exerts a huge influence in the whole life cycle of plants, especially stress-resistance responses. With the development of functional genomics, that the action mechanism of ethylene takes part in mediated plant architecture has been clarified gradually, such as plant roots, stems, leaves, fiber elongation and so on. Accordingly, the application of ethylene on crops chemical control and genetic improvement is greatly expanded. From the view of ethylene mediated plant architecture in crops, here reviewed advances in ethylene biosynthesis and signal transduction pathway, stress-resistance responses and the yield potential enhance of crops in recently 20 years. On these grounds, the objectives of this paper were to provide scientific reference and a useful clue for the crop creation of ideal plant type.     

Role of ethylene action in ethylene production and poststorage leaf senescence and survival of pelargonium cuttings

This study investigated the role of ethylene action in ethylene production and in poststorage performance of pelargonium cuttings. Cuttings of zonal pelargonium (Pelargonium x hortorum L.H. Bailey) of the cultivars Isabell and Mitzou were treated with ethylene and with the ethylene action inhibitors 1-methylcyclopropene (MCP), silver-thiosulfate (STS) and silver nitrate (SN) and were stored in the dark at different temperatures (5, 12, and 20 °C) for 48 h. Ethylene concentrations in the storage boxes were monitored and poststorage leaf senescence, survival and root formation of cuttings were determined. Applications of MCP resulted in a significant increase of ethylene evolution by cuttings of both cultivars which was more pronounced with increasing storage temperature. After 48 h of storage at 20 °C, ethylene concentrations were more than 20-fold higher for the MCP-treated cuttings as compared to those of the untreated controls. Also preharvest applications of STS and SN increased ethylene evolution by cuttings, even though these effects were less pronounced. However, application of these inhibitors caused severe poststorage leaf injury. Application of ethylene during storage had no effect on subsequent leaf damage. Leaf senescence during rooting and decay of cuttings, which raised with increasing storage temperature, could only partially been reduced by MCP. The results strongly support the conclusion, that in zonal pelargonium cuttings, ethylene production is controlled by autoinhibition, and clearly indicate, that temperature dependent processes other than ethylene action are substantially involved in storage-induced leaf senescence and decay.     

Gene expression profiling in rice young panicle and vegetative organs and identification of panicle-specific genes through known gene functions

In rice, at the stage from pistil and stamen primordia formation to microsporocyte meiosis, the young panicle organs (YPO) make a great contribution to grain productivity. This period corresponds to the onset of meiosis and marks the transition from vegetative to reproductive stages. By comparing gene expression profiling of YPO with that of rice aerial vegetative organs (AVO), it is possible to gain further molecular insight into this period that is developmentally and functionally important. In this report, a total of 92,582 high-quality ESTs from 5′-end sequencing, including 44,247 from YPO and 48,335 from AVO, were obtained and classified. There were 12,884 (29.12%) ESTs from YPO and 16,304 (33.73%) ESTs from AVO matched to known genes, which generated 1,667 and 2,172 known genes, respectively, after integration of these ESTs. From the functions of known homologous genes, we identified some tissue- and developmental-stage-specified genes in YPO. The expression of these genes clearly reflected the unique functional characteristics of YPO. Furthermore, we estimated that there are about 10,000 mRNAs specifically expressed in rice YPO. Jiabin Tang and Hong’ai Xia contributed equally to this work     

Use of proteomics to understand seed development in rice

Rice is an important cereal crop and has become a model monocot for research into crop biology. Rice seeds currently feed more than half of the world's population and the demand for rice seeds is rapidly increasing because of the fast‐growing world population. However, the molecular mechanisms underlying rice seed development is incompletely understood. Genetic and molecular studies have developed our understanding of substantial proteins related to rice seed development. Recent advancements in proteomics have revolutionized the research on seed development at the single gene or protein level. Proteomic studies in rice seeds have provided the molecular explanation for cellular and metabolic events as well as environmental stress responses that occur during embryo and endosperm development. They have also led to the new identification of a large number of proteins associated with regulating seed development such as those involved in stress tolerance and RNA metabolism. In the future, proteomics, combined with genetic, cytological, and molecular tools, will help to elucidate the molecular pathways underlying seed development control and help in the development of valuable and potential strategies for improving yield, quality, and stress tolerance in rice and other cereals. Here, we reviewed recent progress in understanding the mechanisms of seed development in rice with the use of proteomics.     

Comparative analysis of young panicle proteome in thermo-sensitive genic male-sterile rice Zhu-1S under sterile and fertile conditions

Proteome analysis was carried out to identify the young panicle proteins during different developmental stages under sterile and fertile conditions. Based on spot quantity and quality, 50 protein spots were analyzed by matrix associated laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) and 20 spots were identified. Most of these proteins are closely associated with energy metabolism, protein biosynthesis, cell wall formation and stress responses, which are essential cell activities to the pollen development. Gene expression analysis of three different proteins by semi-quantitative RT-PCR showed that the mRNA level was not correlated exactly with the protein level.     

ABERRANT PANICLE ORGANIZATION 1 temporally regulates meristem identity in rice

We report a recessive mutation of rice, aberrant panicle organization 1 (apo1), which severely affects inflorescence architecture, floral organ identity, and leaf production rate. In the wild-type inflorescence, the main-axis meristem aborts after forming 10-12 primary branch primordia. However, in apo1, the main-axis meristem was converted to a spikelet meristem after producing a small number of branch primordia. In addition, the branch meristems in apo1 became spikelet meristems earlier than in wild type. Therefore, in the inflorescence, the apo1 mutation caused the precocious conversion of the meristem identity. In the apo1 flower, lodicules were increased at the expense of stamens, and carpels were formed indeterminately by the loss of meristem determinacy. Vegetative development is also affected in the apo1. Leaves were formed rapidly throughout the vegetative phase, indicating that APO1 is also involved in temporal regulation of leaf production. These phenotypes suggest that the APO1 plays an important role in the temporal regulation of both vegetative and reproductive development.     

Light-dependent production of ethylene in Tillandsia usneoides L.

Tillandsia usneoides L. is a favorite model plant for investigating ethylene biosynthesis because no soil is needed for cultivation (important for long-term measurements) and small plants and different clones are available. We investigated the endogenous production of ethylene in relation to temperature, light, daylength and CO₂ concentration. Using a novel and most sensitive technique to measure ethylene, laser-driven photoacoustic spectroscopy, real-time online measurements were performed. Since T. usneoides is a crassulacean acid metabolism (CAM) plant and does not take up CO₂ during the day we could show that ethylene production is strictly light dependent and does not follow any endogenous rhythm. In contrast to reports on other plants, CO₂ concentration did not influence the production of ethylene by T. usneoides. However, high ethylene production was obtained after application of 1-aminoacyclopropane-1-carboxylic acid (ACC). Received: 10 September 1997 / Accepted: 27 November 1997     

Morphological analysis of seed shape in Arabidopsis thaliana reveals altered polarity in mutants of the ethylene signaling pathway

The shape of Arabidopsis thaliana dry seed is described here as a prolate spheroid. The accuracy of this approximation is discussed. Considering its limitations, it allows a geometric approximation to the analysis of changes occurring in seed shape during imbibition prior to seed germination as well as the differences in shape between genotypes and their changes during imbibition. The triple mutant ein2-1, ers1-2, etr1-7 presents notable alterations in seed shape. In addition, seeds of this and other mutants in the ethylene signaling pathway (ctr1-1, eto1-1, etr1-1, ein2-1) show different response to imbibition than the wild type. Imbibed seeds of the wild type increase their asymmetry compared with the dry seeds. This is detected by the relative changes in the curvature values in both poles. Thus, during imbibition of the wild-type seeds, the reduction in curvature values observed in the basal pole gives them an ovoid shape. In contrast, in the seeds of the ethylene mutants, reduction in curvature values occurs in both basal and apical poles, and its shape remains as a prolate spheroid. Our data indicate that the ethylene signaling pathway is involved, in general, in the complex regulation of seed shape and, in particular, in the establishment of polarity in seeds, controlling curvature values in the seed poles.     

OsGRF4 controls grain shape,panicle length and seed shattering in rice

Traits such as grain shape, panicle length and seed shattering, play important roles in grain yield and harvest. In this study, the cloning and functional analysis of PANICLE TRAITS 2 (PT2), a novel gene from the Indica rice Chuandali (CDL), is reported. PT2 is synonymous with Growth‐Regulating Factor 4 (OsGRF4), which encodes a growth‐regulating factor that positively regulates grain shape and panicle length and negatively regulates seed shattering. Higher expression of OsGRF4 is correlated with larger grain, longer panicle and lower seed shattering. A unique OsGRF4 mutation, which occurs at the OsmiRNA396 target site of OsGRF4, seems to be associated with high levels of OsGRF4 expression, and results in phenotypic difference. Further research showed that OsGRF4 regulated two cytokinin dehydrogenase precursor genes (CKX5 and CKX1) resulting in increased cytokinin levels, which might affect the panicle traits. High storage capacity and moderate seed shattering of OsGRF4 may be useful in high‐yield breeding and mechanized harvesting of rice. Our findings provide additional insight into the molecular basis of panicle growth.