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28 November 2014, Volume 21 Issue 6 Previous Issue    Next Issue
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Selection of Reference Genes for Gene Expression Analysis in Nilaparvata lugens with Different Levels of Virulence on Rice by Quantitative Real-Time PCR WANG Wei-xia, LAI Feng-xiang, LI Kai-long, FU Qiang 2014, 21(6): 305-311.  DOI: 10.1016/S1672-6308(14)60272-9 Abstract ( )   PDF (29870KB) ( )   The brown planthopper Nilaparvata lugens St?l (Homoptera: Delphacidae) can cause hopperburn by feeding on rice and also can transmit the grassy stunt disease. Resistant rice varieties have been developed, but several N. lugens strains can recover their virulence to these resistant rice varieties. In the present study, reference genes with stable expression levels in N. lugens populations showed different levels of virulence to susceptible and resistant rice varieties. The expression of six candidate reference genes in N. lugens feeding on susceptible and resistant rice varieties was analyzed. These genes were evaluated for their potential use in the analysis of differential gene expression. Polymerase chain reaction data was generated from N. lugens, including two different treatments (resistant or susceptible rice) and three virulent N. lugens populations. Three software programs (BestKeeper, Normfinder and geNorm) were used to assess the candidate reference genes. Both geNorm and Normfinder identified the genes 18S, β-ACT, β-TUB and α-TUB as the most stable reference genes. BestKeeper identified ETIF1 as the optimal reference gene with the least overall variation, whereas 18S and α-TUB were the second and third most stably expressed genes, respectively. Therefore, we concluded that the genes 18S and α-TUB were the most suitable reference genes in N. lugens. These results will facilitate future transcript profiling studies on N. lugens populations that show variation in virulence levels on different rice varieties.

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Reverse Genetic Analysis of Transcription Factor OsHox9, a Member of Homeobox Family, in Rice AI Li-ping, SHEN Ao, GAO Zhi-chao, LI Zheng-long, SUN Qiong-lin, LI Ying-ying, LUAN Wei-jiang 2014, 21(6): 312-317.  DOI: 10.1016/S1672-6308(14)60271-7 Abstract ( )   PDF (3286KB) ( )   Homeobox transcription factors participate in the growth and development of plants by regulating cell differentiation, morphogenesis and environmental signal response. To reveal the functions of these transcription factors in rice, we constructed the RNAi vectors of OsHox9, a member of homeobox family, and analyzed the function of OsHox9 using reverse genetics. The plant height and tillering number of RNAi transgenic plants decreased compared with those of wild-type plants. Reverse transcription-polymerase chain reaction analysis showed that OsHox9 expression reduced in the transgenic plants with phenotypic variance, whereas that in the transgenic plants without phenotypic variance was similar to that in the wild-type plants. This result suggests that the phenotypes of the transgenic plants were caused by RNAi effects. The tissue-specificity of OsHox9 expression indicated that it was expressed in different organs, with high expression in stem apical meristem and young panicles. Subcellular location of OsHox9 demonstrated that it was localized on the cell membrane.

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Improvement of Rice Resistance to Sheath Blight by Pyramiding QTLs Conditioning Disease Resistance and Tiller Angle ZUO Shi-min, ZHANG Ya-fang, CHEN Zong-xiang, JIANG Wei, FENG Ming-hui, PAN Xue-biao 2014, 21(6): 318-326.  DOI: 10.1016/S1672-6308(14)60274-2 Abstract ( )   PDF (149KB) ( )   Rice resistance to sheath blight (SB) is controlled by polygenes or quantitative trait loci (QTLs) and affected by plant morphological traits. qSB-9TQ and TAC1TQ, which control SB resistance and tiller angle (TA), respectively, were employed to test whether the combination of the two genes will further improve rice SB resistance and reduce yield loss rather than only one of them or neither. Using two pairs of near isogenic lines (NILs), TAC1TQ was confirmed to contribute to SB resistance. However, its effect was less considerable than that of qSB-9TQ. Subsequently, the two genes were introduced into two commercial rice varieties to develop a series of NILs. The NILs carrying both TAC1TQ and qSB-9TQ showed more resistance than the NILs containing only one of them. Comparing the grain yield per plant (GYP) under the three different SB disease conditions, namely slight, moderate and severe conditions, NILs carrying both genes apparently lost lower GYP than the NILs without the two genes and the NILs carrying only TAC1TQ. Under slight disease condition, no significant differences were found on morphology, development and GYP associated traits except for TA between the NILs carrying both genes and either of them, indicating that the two genes have no inferior effect on rice agronomic traits. Results indicated that TAC1TQ and qSB-9TQ have high breeding potential, and pyramiding SB resistance QTL and morphological trait QTL is a potential approach in improving rice SB resistance.

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Selenium Accumulation and Antioxidant Status of Rice Plants Grown on Seleniferous Soil from Northwestern India Sucheta SHARMA, Reeti GOYAL, Upkar Singh SADANA 2014, 21(6): 327-334.  DOI: 10.1016/S1672-6308(14)60270-5 Abstract ( )   PDF (1824KB) ( )   Greenhouse experiment was conducted to investigate selenium accumulation and its antioxidant response in two rice varieties (PR116 and Pusa Basmati 1121) grown on normal and seleniferous soils. The plant growth was reduced at early developmental stages and flowering was delayed by a period of 10 d on seleniferous soil. Selenium accumulation increased by 3–20 and 13–14 folds in leaves, 18 and 3 folds in grains from Pusa Basmati 1121 and PR116 varieties, respectively. Selenium accumulation in leaves from rice plants grown on seleniferous soil resulted in significant increase in chlorophyll content, hydrogen peroxide, proline, free amino acids, total phenol and tannin contents. Lipid peroxidation levels and peroxidase activities in leaves increased whereas catalase activity showed a reverse trend. It is concluded that selenium accumulation decreased dry matter content in rice during crop development but these plants were able to combat selenium toxicity by inducing alterations in their defense system.

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Photosynthetic Characteristics of Flag Leaves in Rice White Stripe Mutant 6001 During Senescence Process ZHEN Xiao-hui, XU Jin-gang, SHEN Wei-jun, ZHANG Xiao-juan, ZHANG Qi-jun, LU Chuan-gen, CHEN Guo-xiang, GAO Zhi-ping 2014, 21(6): 335-342.  DOI: 10.1016/S1672-6308(14)60268-7 Abstract ( )   PDF (113762KB) ( )   Physiological, biochemical and electron microscopy analyses were used to investigate the photosynthetic performance of flag leaves in rice white stripe mutant 6001 during the senescence process. Results showed that the chlorophyll content at the heading and milk-ripe stages in rice mutant 6001 were about 34.78% and 3.00% less than those in wild type 6028, respectively. However, the chlorophyll content at the fully-ripe stage in rice mutant 6001 was higher than that in wild type 6028. At the heading stage, the net photosynthetic rate (Pn) in rice mutant 6001 was lower than that in wild type 6028. Rice mutant 6001 also exhibited a significantly slower decrease rate of Pn than wild type 6028 during the senescence progress, especially at the later stage. Furthermore, Ca2+-ATPase, Mg2+-ATPase and photophosphorylation activities exhibited the similar trends as the Pn. During the senescence process, the 68 kDa polypeptide concentrations in the thylakoid membrane proteins exhibited a significant change, which was one of the critical factors that contributed to the observed change in photosynthesis. We also observed that the chloroplasts of rice mutant 6001 exhibited higher integrity than those of wild type 6028, and the chloroplast membrane of rice mutant 6001 disintegrated more slow during the senescence process. In general, rice mutant 6001 had a relatively slower senescence rate than wild type 6028, and exhibited anti-senescence properties.

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Temporal Dynamics of Antioxidant Defence System in Relation to Polyamine Catabolism in Rice under Direct-Seeded and Transplanted Conditions Manisha KUMARI1, Bavita ASTHIR1, Navtej Singh BAINS2 2014, 21(6): 343-353.  DOI: 10.1016/S1672-6308(13)60195-X Abstract ( )   PDF (7927KB) ( )   Six rice cultivars viz. PR120, PR116, Feng Ai Zan, PR115, PAU201 and Punjab Mehak 1 under the direct-seeded and transplanted conditions were used to investigate the involvement of antioxidative defence system in relation to polyamine catabolism in temporal regulation of developing grains. Activities of ascorbate peroxidase (APx), guaiacol peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), polyamine oxidases (PAO) and contents of ascorbate, α-tocopherol, proline and polyamines increased gradually until mid-milky stage and then declined towards maturity stage under both planting conditions. The transplanted condition led to higher activities of antioxidative enzymes (APx, GPx and CAT) and contents of ascorbate, α-tocopherol and proline whereas the direct-seeded condition had elevated levels of PAO and SOD activities and contents of polyamines, lipid peroxide and hydrogen peroxide. Cultivars Feng Ai Zan and PR120 exhibited superior tolerance over other cultivars by accumulating higher contents of ascorbate, α-tocopherol and proline with increasing level of PAO and SOD activities under the direct-seeded condition. However, under the transplanted condition PR116 and PAU201 showed higher activities of antioxidative enzymes with decreasing content of lipid peroxide. Therefore, we concluded that under the direct-seeded condition, enhancements of polyamines content and PAO activity enabled rice cultivars more tolerant to oxidative stress, while under the transplanted condition, antioxidative defence with decreasing of lipid peroxide content was closely associated with the protection of grains by maintaining membrane integrity during rice grain filling. The results indicated that temporal dynamics of H2O2 metabolic machinery was strongly up-regulated especially at the mid-milky stage.

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Integrated Approach to Control False Smut in Hybrid Rice in Sichuan Province, China LIANG Yan, ZHANG Xue-mei, LI De-qiang, HUANG Fu, HU Pei-song, PENG Yun-liang 2014, 21(6): 354-360.  DOI: 10.1016/S1672-6308(14)60269-9 Abstract ( )   PDF (732KB) ( )   Severe epidemic of false smut, caused by Ustilaginoidea virens (Cooke) Takahashi (teleomorph Villosiclava virens) has been reported in different parts of Asia and America. Different fungicides or bio-control agents against false smut were applied at different times before heading on a susceptible rice variety Pu-6. A control efficiency as high as 91.92% was resulted from spraying 2.5% Wenquning, a suspension of Bacillus subtilis in solution of validamycin with 4.5 L/hm2 at 6 d before heading. Among the 186 hybrid rice screened in 2010, low significant correlations between the dates of full heading, rates of infected plants and panicles as well as the number of infected florets were found, with the correlation coefficients ranging from 0.2331 to 0.5212. However, significant difference in susceptibility coefficients was also found between the varieties which had the same dates of full heading. In the plot experiments to compare the susceptibility in 2011, the average rates of infected panicles of Yixiangyou 2168, Chuanxiangyou 3, Dexiang 4103, Yixiangyou 2115, Nei5you 317, Yangxinyou 1 were significantly lower than those of the control varieties Gangyou 725 and Gangyou 188 at the disease nursery located at Qionglai, Sichuan Province, China. When Neixiangyou 8156 and Nei5you 317 were sprayed with 2.5% Wenquning at 4.5 L/hm2 for two times at 6 d before and 1 d after heading, respectively, the control efficiencies of Nei5you 317 and Neixiangyou 8156 were respectively 100% and 82.24% compared to that of Gangyou 725. Satisfactory control effects had also obtained by single spray of 2.5% Wenquning at 4.5 L/hm2 at 5–6 d before heading. Therefore, less susceptible hybrid rice in combination with spraying Wenquning at 5–6 d before heading was suggested for the disease control in Sichuan Province, China.