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10 September 2018, Volume 32 Issue 5 Previous Issue    Next Issue
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The Guanylate Kinase OsGK1 is Essential for Seed Development in Rice Jingfang LI, Yunlu TIAN, Xi LIU, Shijia LIU, Liangming CHEN, Ling JIANG, Wenwei ZHANG, Dayong XU, Yihua WANG, Jianmin WAN 2018, 32(5): 415-426.  DOI: 10.16819/j.1001-7216.2018.8003 Abstract ( )   HTML ( )   PDF (2443KB) ( )   【Objective】In this study, the phenotype of the floury and shrunken endosperm mutant fse2 was analyzed. Isolation of the responsible gene will lay a foundation for elucidating the mechanism underlying starch synthesis and embryo development in rice. 【Method】fse2 was obtained from the mutant library of japonica cultivar Dianjingyou 1 induced with N-Nitroso-N-methylurea. In this study, the physiochemical properties of fse2 endosperm were investigated and the structure of starch grains was observed. An F2 population derived from fse2 and N22 was constructed, then the underlying gene was determined by map-based cloning and complementation tests. qRT-PCR and GUS staining were used to analyze the expression of FSE2. Western blotting was performed to analyze the protein levels of starch synthesis related genes and mitochondrial genes in the mutant. 【Result】Compared with the transparent endosperm of wild type, fse2 displayed a floury and shrunken endosperm, significantly declined 1000-grain weight, smaller and loosely packed irregular compound starch grains. Total starch and amylose content decreased significantly, while the lipid content increased obviously in fse2, and the gelatinization characteristics of fse2 were changed notably. FSE2 encodes a guanylate kinase named OsGK1, which is dual-targeted to both mitochondria and plastids. OsGK1 was constitutively expressed in various organs with the highest level in developing endosperm at 6th day after flowering. The protein levels of most of the starch synthesis related genes in the mutant endosperm were significantly decreased, especially AGPS2b and PHOI. In addition, the homozygous seeds of fse2 were lethal and the development of fse2 embryos was severely arrested. The accumulation of mitochondria AOX was notably elevated, while almost undetectable in the wild type, indicating the mitochondrial respiratory chain was impaired. 【Conclusion】Due to the functional defects of OsGK1, the development of mitochondria and amyloplasts are abnormal, leading to the embryo lethality and a floury and shrunken endosperm.

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Expression Patterns and Regulation of Transcription Factor Gene OsSHR2 in Vegetative Growth in Rice Zhantian ZHANG, Yafei SUN, Hao AI, Wenzhen LUO, Bing FENG, Wenxian SUN, Guohua XU, Shubin SUN 2018, 32(5): 427-436.  DOI: 10.16819/j.1001-7216.2018.7037 Abstract ( )   HTML ( )   PDF (1303KB) ( )   【Objective】OsSHR2(LOC_Os03g31880) is a homologous gene of AtSHR of Arabidopsis thaliana, which falls into GRAS transcription factor family together with OsSHR1, OsSCR1 and OsSCR2 in rice. It has been reported that the transcription factor genes SHR and SCR regulate the development of roots and leaves, and participate in various life activities. We analyzed the temporal and spatial expression patterns and the way OsSHR2 regulates vegetative growth in rice.【Method】The function of OsSHR2 was verified by bioinformatics analysis, expression pattern analysis, germination kinetic analysis and hydroponic experiments.【Result】 Biomechanical analysis showed that OsSHR2, OsSHR1, OsSCR1 and OsSCR2 had high homology with SHR subfamily and SCR subfamily in Arabidopsis thaliana and other species. The expression pattern analysis by qRT-PCR and pOsSHR2::GUS staining showed that OsSHR2 was strongly expressed in the roots, leaves, vascular tissues and reproductive organs during the whole vegetative and reproductive growth stages, and especially in the stele of the root tip, lateral root primordium and the central of leaf and stem vascular tissue. Additionally, the relative expression of OsSHR2 was down-regulated in Pi-deficiency in shoots and roots of wild type. The seed germination and hydroponic experiment analysis of CRISPR-Cas9 mutant osshr2 showed that seed germination of osshr2 was delayed and with lower germination rate than that of WT, in addition the length of shoot and root of osshr2 were significantly shorter than WT under Pi-sufficient and Pi-deficient conditions.【Conclusion】OsSHR2 plays an important role in the development of shoots and roots, the formation of vascular tissue and various activity in vegetative and reproductive growth, which lays an important theoretical basis for the application of OsSHR2 in molecular breeding.

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Functional Analysis of a Copper/Zinc SOD Encoding Gene in Response to Arsenite Stress in Rice Lingling DOU, Haichao HU, Long MA, Xiaonan KE, Mingyue LIU, Wangmin LIAN, Ke JIN, Lingjuan XIE, Qingpo LIU 2018, 32(5): 437-444.  DOI: 10.16819/j.1001-7216.2018.7154 Abstract ( )   HTML ( )   PDF (703KB) ( )   【Objective】Os08g44770.1 encodes a Cu/Zn-SOD protein in rice, but its biological function in response to arsenite [As(Ⅲ)] remains unclear. The results presented here would be intriguing for further investigating the molecular mechanisms of Os08g44770.1-mediated arsenic tolerance in rice, and also providing useful new idea for rice stress resistance breeding. 【Methods】Using wild type(WT) Nipponbare and two transgenic rice lines overexpressing Os08g44770.1 as materials, we investigated the phenotypes of WT and transgenic plants after exposure to As(Ⅲ), and further uncovered its physiological and molecular mechanisms in regulation of As(Ⅲ) tolerance in rice through stress treatment, physiological index measurement, and gene expression analysis, etc. 【Result】The results showed that, compared with WT, transgenic rice plants were more sensitive to As(Ⅲ) stress; Under As(Ⅲ) exposure, transgenic plants showed shorter relative root elongation, lower biomass (dry weight) and chlorophyll content, as well as lower root cell membrane integrity and antioxidant abilities in leaves. Moreover, Os08g44770.1 exhibited slightly different expression patterns but both showing expression peak at 24 h after As(Ⅲ) treatment in leaves of WT and transgenic plants. 【Conclusion】Strong overexpression of Os08g44770.1 in rice would result in its hypersensitivity to arsenite stress.

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Improving the Ability of C418 to Restore the Fertility of the Honglian-type Cytoplasmic Male Sterility japonica Lines via Molecular Marker-assisted Selection Honggen ZHANG, Chongyuan ZHONG, Hua SI, Qiaoquan LIU, Minghong GU, Shuzhu TANG 2018, 32(5): 445-452.  DOI: 10.16819/j.1001-7216.2018.7152 Abstract ( )   HTML ( )   PDF (551KB) ( )   【Objective】Efficient breeding of japonica restorers for Honglian(HL) type japonica cytoplasmic male sterile(CMS) lines is vital to develop HL-type japonica hybrids, which is of great significance for the development of three-line japonica hybrids.【Method】Rf6, a fertility restorer gene for HL-type CMS, was identified from ‘9311’, an indica restorer for HL-type CMS lines. In our previous study, R1093, a chromosome segment substitution line derived from the cross between the donor parent ‘9311’and the recipient parent ‘Nipponbare’, had been identified to carry Rf6. In the present study, Rf6 was pyramided into C418, a BT-type japonica restorer only carrying Rf1, using backcross via marker-assisted selection, and the restoration ability of the improved lines for BT-, HL-type CMS lines was analyzed by testcrossing.【Result】To 2016, a total of 67 improved lines, including 12 BC3F4 lines and 55 BC4F3 lines, had been obtained, and most of the agronomic traits were well maintained in six improved lines. The testcrossed F1 plants from improved lines and BT-Liuqianxin A exhibited the similar fertility levels with those of the testcrossed F1 plants from C418. The significant increased fertility levels were observed on the testcrossed F1 plants from improved lines and HL-Liuqianxin A, and most of these testcrossing lines exhibited fertility levels over 85%, indicating these improved lines can be applied to rice production.【Conclusions】The pyramiding of Rf6 and Rf1 can improve the restoration ability of BT-type japonica restorer lines to HL-type japonica CMS lines, which should be an important way to breed HL-type japonica restorer lines.

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Development of Specific Markers for Pigm in Marker-Assisted Breeding of Panicle Blast Resistant japonica Rice Shengyuan ZENG, Chuang LI, Cancan DU, Liting SUN, Dedao JING, Tianzi LIN, Bo YU, Huafei QIAN, Weicheng YAO, Yiwen ZHOU, Hongbing GONG 2018, 32(5): 453-461.  DOI: 10.16819/j.1001-7216.2018.7135 Abstract ( )   HTML ( )   PDF (2128KB) ( )   【Objective】 Pigm is a broad-spectrum resistance gene to rice blast, which is isolated from Gumei 4, a variety with durable resistance. Pigm is allelic to Piz, Piz-t, Pi2, Pi9, Pi40 and so on, but shows different resistance spectrum. To breed resistance variety carrying Pigm with molecular marker-assisted selection, discovering Pigm-tightly-linked markers is important.【Method】We identified a unique DNA sequence of Gumei 4 by genomic sequencing, and developed a set of specific markers tagged to Pigm base on the sequence divergence. Then, by means of molecular-assisted selection and background gene screening, Pigm was pyramided to three representative japonica varieties belonging to different ecotypes from Yangtze-Huai River Area. 【Result】 An InDel marker Pigm-4 which is closely linked to the functional unit of Pigm was developed. Pigm-4 showed distinct specificity by genotype screening of various rice varieties, and can distinguish the genotype of Pigm from its alleles Piz, Piz-t, Pi2, Pi9 and Pi40. Although receptors carry with resistant genes such as Pib+Pi54 (Wuyun 2674), Pib+Pita (Wuyunjing 27), Pib+Pi54+Pb1 (Zhendao 18), respectively, but none of them can defense high virulence blast pathogen. Relevant introgression lines were established and inoculations of introgression lines indicate that Pigm can promote resistance level to rice panicle blast significnatly in different japonica backgrounds. 【Conclusion】Pigm can be used as a beneficial gene source in the breeding of blast resistant japonica rice, and Pigm-4 is an excellent marker for the molecular marker-assisted selection of Pigm.

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Study on Yield Formation and Population Quality of indica Hybrid Rice with Good Quality and High Yield Under Mechanical Direct Seeding Changchun GUO, Zhibai SUN, Yongjian SUN, Yaozhu YIN, Yunxia WU, Yuan TANG, Zhiyuan YANG, Kaihong XIANG, Jun MA 2018, 32(5): 462-474.  DOI: 10.16819/j.1001-7216.2018.8016 Abstract ( )   HTML ( )   PDF (476KB) ( )   【Objective】Our aim is to explore the common characteristics of high-yielding and high quality indica hybrid rice varieties suitable for mechanical direct seeding in plain (Chongzhou) and hilly (Santai) areas and establish a standardized selection method and evaluation criteria for it, which could lay a theoretical and practical basis for the integration of hybrid indica rice mechanized seeding technology.【Method】Twenty-nine indica hybrid rice combinations were used as materials in two ecological zones, artificial simulated mechanized precise hill-seeding (mechanical direct seeding for short), and the effects of mechanical direct seeding on the population quality characteristics and yield of high-quality indica hybrid rice with different yield levels in plain and hilly areas were studied, the relationship between population quality characteristics and yield of high-quality indica hybrid rice combinations by mechanical seeding was also discussed.【Results】The results showed that, by cluster analysis based on average grain yield of each cultivars in the two areas, the 29 tested combinations could be classified into three groups: high-yielding, mid-yielding, and low-yielding. In the total tested cultivars, high-yielding combinations from Santai accounted for 17.24%, and other types covered 82.76%, high-yielding varieties from Chongzhou were 10.34%, and other types were 89.66%. Compared with the middle-yield and low-yielding varieties, the common high yielding varieties were featured by strong tillering ability, more effective panicles, higher seed-setting rate, higher leaf area index(LAI) after jointing stage and higher dry matter accumulation, moreover, its leaf length, leaf position, leaf opening angle of top three, plant height, top light energy intercept during filling exceled obviously. In addition to population light transmittance, leaf opening angle, tillering LAI and dry matter accumulation, correlation analysis indicated that there existed significantly or highly significantly positive correlations (r=0.37*-0.90**) between index of population quality and yield under mechanical direct-seeding, especially between high efficiency LAI rate at full heading, dry matter accumulation at maturity, and harvest index and yield.【Conclusion】High-yielding varieties have higher panicle and grain number per panicle, and seed-setting rate and high growth at late growth stage. That is how it can obtain higher yields under mechanical direct-sowing.

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Effects of Nitrogen Fertilizer Application on Starch Quality, Activities and Gene Expression Levels of Related Enzymes in Rice Endosperm Tao SUN, Laga TONG, Shuyu ZHAO, Haiwei WANG, Yunfei HAN, Zhongchen ZHANG, Zhengxun JIN 2018, 32(5): 475-484.  DOI: 10.16819/j.1001-7216.2018.8013 Abstract ( )   HTML ( )   PDF (395KB) ( )   【Objective】The research aims to lay a theoretical basis for clarifying the influencing mechanism of nitrogen fertilization during grain filling period on rice starch quality.【Method】Four japonica rice varieties with significant difference in amylose content in grains were selected. Pot experiments were conducted to study the effect of nitrogen application on the starch component and protein content in rice grains, and the protein hydrolysis of rice grains on starch viscosity properties, and to analyze the effect of nitrogen nutrition on the activity of sucrose synthase(SuSy), sucrose phosphate synthase(SPS) and acid invertase(AI) and the mRNA expression levels of OsGBSSⅠ, OsISAⅠ, OsSBEⅠand OsSBEⅡ genes of rice grains during grain filling period.【Results】The results showed that the grain amylopectin content was sensitive to nitrogen nutrition, and nitrogen nutrition during grain filling period changed the content of starch components in grains. The cooking and eating quality of high amylose content varieties degraded even more. The removal of rice protein could significantly improve the viscosity of rice, and the starch composition had a great influence on the viscosity properties of rice starch. Increasing nitrogen nutrition at grain filling stage significantly or highly significantly increased the activity of SuSy and AI in grains, and significantly inhibits the activity of SPS. The nitrogen nutrition at grain filling stage changed the mRNA expression level of OsGBSSⅠ, OsISAⅠ and OsSBEⅡ of rice grains at different stages of grain filling, so that the change dynamics of the mRNA expression quantity of these genes changed during grain filling period except OsSBEⅠ. Due to the influence of nitrogen nutrition, at the beginning of grain filling, OsGBSSⅠ expression level was upregulated significantly, but downregulated significantly in the middle and late stages of grain filling. Nitrogen fertilization could significantly inhibit the transcription expression quantity of OsISAⅠ of grains at grain filling stage and OsSBEⅠ of grains in the middle and late stages of grain filling, and could significantly improve the mRNA expression quantity of OsSBEⅠ of grains in the early and middle stages of grain filling. Nitrogen nutrition could inhibit the transcription expression quantity of OsSBEⅡ gene of grains at the beginning of grain filling, and improve the transcription expression quantity of genes in the middle and late stages of grain filling.【Conclusion】In addition to the effect of protein content on starch quality during grain filling and ripening, nitrogen nutrition also affected starch content and fine structure by regulating enzyme activities and gene expression related to starch synthesis. Ultimately, it changed the rice viscosity and taste quality.

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Effects of Plant Growth-promoting Rhizobacteria(PGPR) on Physiological Characteristics of Rice Under Drought Stress Su CHEN, Jiankun XIE, Wenxin HUANG, Dengyun CHEN, Xiaojian PENG, Xueqin FU 2018, 32(5): 485-492.  DOI: 10.16819/j.1001-7216.2018.7123 Abstract ( )   HTML ( )   PDF (340KB) ( )   【Objective】This study aims to reveal the effects of plant growth-promoting rhizobacteria Bacillus cereus F06 on physiological characteristics of the rice Shanyou 63 under different drought stress treatments(light, moderate, severe and a control).【Method】The combined effects of F06 inoculation and various levels of drought stress on the photosynthetic characteristics, chlorophyll fluorescence parameters, cytokinin and abscisic acid(ABA) concentrations, relative water content,and relative electrolyte leakage were studied in a pot experiment. 【Result】The results showed that Pn and gs decreased with increasing drought stress. However, F06 inoculation significantly slowed down the decrease of Pn and gs under drought stress compared with non-inoculation(NP) treatment, Pn and gs increased by 7.67%, 12.97%, 18.14% and 11.51%, 16.63% and 17.07%, respectively. With the intensifying drougnt stress, it followed an increasing trend. F06 inoculation inhibited the decrease of Fv/ Fm and qP and the increase of Fo, NPQ and improved the light conversion efficiency of rice leaves significantly under drought stress. Under the drought stress, B.cereus F06 inoculation could reduce the change amplitude of leaf water potential, relative water content and relative conductivity. However, F06 inoculation could not reverse the decrease trend of leaf water potential,relative water content and relative conductivity. F06 inoculation also significantly depressed the pigment decomposition or reduction. Although no significant increase was observed under well-watered conditions, drought significantly reduced the cytokinin(CTK) content in leaves and roots of rice, and increased ABA content in leaves, but F06 inoculation significantly increased the cytokinin content of drought-stressed leaves and roots Shanyou 63. 【Conclusion】In conclusion,inoculation of PGPR could reduce the decomposition or loss of photosynthetic pigments and improve the photosynthetic rate,showing real potential for practical use in arid environments as a drought stress inhibitor．

实验技术

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Detection of Seed-borne Rice Bakanae Pathogens in Jiangsu Province, China Using Loop-mediated Isothermal Amplification Assays Yongtian YUAN, Zhenyang RONG, Wenwu YE, Hongsheng ZHANG, Yiqing ZHUANG, Xiaobo ZHENG 2018, 32(5): 493-500.  DOI: 10.16819/j.1001-7216.2018.7119 Abstract ( )   HTML ( )   PDF (410KB) ( )   【Objective】The research aims to reveal the situation of seed-borne rice bakanae pathogens in Jiangsu Province, China. 【Methods】The seeds of 65 major rice cultivars collected from this area were analyzed by using loop-mediated isothermal amplification (LAMP) assays for specific detection of 4 known rice bakanae pathogen species, including Fusarium fujikuroi, F. proliferatum, F. verticilliodes and F. andiyazi. 【Results】There were 54 rice cultivars carrying rice bakanae pathogens, indicating it’s a common phenomenon that rice seeds carrying rice bakanae pathogens in Jiangsu Province. And the most frequent species was F. fujikuroi, representing 83.07% of the total samples tested, followed by F. proliferatum and F. andiyazi, representing 10% and 6% respectively. However, none of the 65 rice cultivars was tested to be carrying F. verticilliodes. 【Conclusions】The method is readily available for detecting seed-borne rice bakanae pathogens.

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Physiological Changes in Rice Plants After Infestation by Whitebacked Planthoppers at Different Nitrogen Levels Zaiyuan LI, Bo XU, Fulian WANG, Xiaohai TIAN, Yuekun MA, Yujun ZHONG, Shiyang CHENG 2018, 32(5): 501-508.  DOI: 10.16819/j.1001-7216.2018.8012 Abstract ( )   HTML ( )   PDF (811KB) ( )   【Objective】In order to clarify the physiological mechanism in regulating the resistance of rice to whitebacked planthoppers at different nitrogen levels,【Method】we compared the differences in contents of chlorophyll, relative water content, bleeding sap, water content, dry matter content, soluble sugar contents in infected rice at different nitrogen levels by indoors cage-raising method.【Result】The results showed that there were significant changes in different defensive substances in rice after infection by whitebacked planthoppers. The contents of chlorophyll, dry matter weight and soluble sugar contents in rice plants decreased after BPH infection, while the content of bleeding sap, relative water content and water content increased. With increasing nitrogen levels, chlorophyll (SPAD) contents and dry matter weight of rice increased, and the increase of water content and bleeding sap content followed an upward trend. Water content, soluble sugar contents were on a decreasing trend. 【Conclusion】Nitrogen level could affect the resistance of rice to whitebacked planthoppers by regulating the contents of chlorophyll (SPAD), relative water content, water content, dry matter weight and soluble sugar contents in rice, subsequently influencing the population of whitebacked planthoppers.

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Advances in Restoration Effects of Rice Growing on Eutrophic Water Zhiping SUN, Lin QIN, Yaobin LIU, Fengbo LI, Jinfei FENG, Dianxing WU, Fuping FANG 2018, 32(5): 509-518.  DOI: 10.16819/j.1001-7216.2018.8005 Abstract ( )   HTML ( )   PDF (332KB) ( )   Eutrophication is an important factor limiting sustainable development of agriculture in China. Rice has significant capacity to purify eutrophic water. With in-situ and ex-situ remediation technologies, rice planting has great potential in restoration of eutrophic water in lakes, large reservoir, sewage river, fertile water from aquaculture pond, the irrigation return flow and domestic wastewater. With a summary of previous studies, We comprehensively compared the effects of rice planting on the restoration of eutrophic water and the removal efficiency of nutrients, and analyzed the technical characteristic and disadvantages in the application of three modes(floating-bed rice planting, paddy wetland and rice-fish co-culture).