Transgenic rice homozygous lines expressing GNA showed enhanced resistance to rice brown planthopper

Mature seed-derived calli from two elite Chinese japonica rice (Oryza sativa L.) cultivars Eyi 105 and Ewan 5 were co-transformed with two plasmids, pWRG1515 and pRSSGNA1, containing the selectable marker hygromycin phosphotransferase gene (hpt), the reporter β-glucuronidase gene (gusA) and the snowdrop (Galanthus nivalis) lectin gene (gna) via particle bombardment. 61 independent transgenic rice plants were regenerated from 329 bombarded calli. 79% transgenic plants contained all the three genes, revealed by PCR/Southern blot analysis. Western blot analysis revealed that 36 out of 48 gna-containing transgenic plants expressed GNA (75%) at various levels with the highest expression being approximately 0.5% of total soluble protein. Genetic analysis confirmed Mendelian segregation of transgenes in progeny. From the R2 generations whose R1 parent plants showing 3:1 Mendelian segregation patterns, we identified five independent homozygous lines containing and expressing all the three transgenes. Insect bioassay and feeding tests showed that these homozygous lines had significant inhibition to rice brown planthopper (Nilaparvata lugens, BPH) by decreasing BPH survival and overall fecundity, retarding BPH development and declining BPH feeding. These BPH-resistant lines have been incorporated into rice insect resistance breeding program. This is the first report that homozygous transgenic rice lines expressing GNA, developed by genetic transformation and through genetic analysis-based selection, conferred enhanced resistance to BPH, one of the most damaging insect pests in rice.     

Diversity and high nitrogenase activity of endophytic diazotrophs isolated from Oryza rufipogon Griff.

Diversity and nitrogenase activity of endophytic diazotrophs colonized in the wild rice Oryza rufipogon Griff grown in Boluo, Huilai County in Guangdong Province and Lingshui County in Hainan Province were studied. Thirty-seven isolates obtained from Oryza rufipogon were identified as putative endophytic nitrogen-fixing bacteria by ARA （acetylene reduction assay） test and further confirmed by PCR amplification of nifH gene fragments. All obtained strains have ARA activity and the same sized nifH gene fragments. Above the similarity level of 80%, the obtained isolates were assigned as Group Ⅰ to Ⅷ by the clustering of IS-PCR fingerprints. The SDS-PAGE whole-cell protein patterns were similar to those of IS-PCR fingerprints. Components and contents of fatty acid methyl esters （FAMEs） were used to differentiate the representative strains （Ls13, Ls8, BL1, BL12, HL6, Ls4） from Group Ⅰ to Group Ⅵ. The six representative strains showed significant difference in contents and components of cellular fatty acid methyl ester. 16S rDNA sequencing analysis showed that strains of Group Ⅰ to Ⅶ were located in Enterobacteraceae （y-proteobacteria）. Strains of Group Ⅰ and Group Ⅱ were closely related to Klebsiella sp.; Strain Ls8 of Group Ⅱ was a little far away from the genus of Pantoea （homology level 96% with Pantoea agglomerans）, which may represent a new species or genus in Enterobacteraceae; Strains of Groups Ⅳ and Ⅴ belonged to different Enterobacter sp.; Strain Ls4 and Ls 9 representing Group Ⅵ were close to Citrobacter amalonaticus with 98% sequence similarity; Strain Ls15 of Group Ⅶ showed 98% sequence identity with Pantoea sp.; Strains of Group Ⅷ were assigned to the genus Ideonella （β-proteobacteria）. Based on the above results, endophytic diazotrophs isolated from O. rufipogon showed great diversity and some diazotrophs showed high nitrogenase activity with 42.52 μmol/mL. h C2H4. Inoculation to rice tests indicated that the isolated endophytic diazotrophs significantly promoted the rice growth.     

一种简单方法提高原生质体再生植株频率

发展了一种简单有效的方法,提高从灿稻品种Ｐｕｓａ Ｂａｓｍａｔｉ１建立的超过１年龄悬浮细胞系中游离的原生质体再生植株频率。两步再生法,即先将愈伤组织转入含高浓度琼脂糖（１０ｇ／Ｌ）的再生培养基中培养后再转入含低浓度琼脂糖（４ｇ／Ｌ）的再生培养基中培养,有助于植株再生,两步再生法结合使用含高浓度激动素Ｋｉｎｅｔｉｎ（１０ｍｇ／Ｌ）的再生培养基,显著提高植株再生频率,利用此法,可使来源于超过１年龄的悬     

Generation of selectable marker-free transgenic rice resistant to chewing insects using two co-transformation systems

To produce selectable marker-free (SMF) transgenic rice resistant to chewing insects, the Bacillus thuringiensis cryIA(c) gene (Bt) was introduced into two elite japonica rice varieties by using two Agrobacterium-mediated co-transformation systems. One system is with a single mini-twin T-DNA binary vector in one Agrobacterium strain, which consists of two separate T-DNA regions, one carrying the Bt while the other contains the selectable marker gene, hygromycin resistant gene (HPT). The other system uses two separate binary vectors in two separate Agrobacterium cultures, containing the Bt or HPT gene on individual plasmids. A lot of independent transgenic rice lines harboring both Bt and selectable marker genes were obtained. The results showed that the co-transformation frequency of the Bt gene and HPT gene was much higher by using the mini-twin T-DNA vector system (29.87%) than that by the two separate binary vector systems (4.52%). However, the frequency of the SMF transgenic rice plants obtained from the offspring of co-transgenic plants (21.74%) was lower for the mini-twin T-DNA vector system than that for the latter (50-60%). The data of ELISA implied that the expressed Bt proteins were quantitated as 0.025-0.103% of total leaf soluble proteins in the transgenic plant. Therefore, several elite transgenic rice lines, free of the selectable marker gene, were chosen. The results from both in vitro and in vivo insect bioassays indicated that the SMF transgenic rice was shown to be highly resistant to the striped stem borer and rice leaf folder. Moreover, in a natural field condition without any insecticide applied, all the transgenic rice plants were found to be not injured by the rice leaf folder, whereas the wild types were impaired seriously.     

北缘普通野生稻实验种群动态研究Ⅰ--克隆生长动态

以江西东乡普通野生稻北缘种群为材料,在当地构建了实验小种群,通过连续的定位跟踪、测定,对普通野生稻种群在各种生境条件下的克隆生长动态进行了长期实验研究．结果表明：(1)不同起始密度水平对普通野生稻生长有影响．较低的起始密度下,无性繁殖率较高,到20枝／m^2时无性生长率降低到一个平衡水平,后不再有明显变化;而较高起始密度的种群,其每月的密度、综合生长量始终较高．(2)轻度放牧对普通野生稻的分蘖株数和综合生长量有一定的抑制作用,但是对无性繁殖率却有一定的刺激作用．(3)长期生长于深水对东乡普通野生稻北缘种群的生长具有抑制作用．     

Transpositional behaviour of the Ds element in the Ac/Ds system in rice

Insertional mutagenesis based on maize Activator/Dissociator (Ac/Ds) transposons is becoming a ma- jor approach used to produce a saturated mutant collection in rice. In this research, Ds-T-DNA trans- formed homozygotes were crossed with Ac-T-DNA transformed homozygotes in order to establish an Ac/Ds transposon system in rice. The successive investigation of Ds transposition from F1 to F5 gen- erations indicated that the frequencies of germinal transposition increased over successive genera- tions and reached 54.2% in F3 generation. The Ds transposition pattern revealed that a Ds transposition induced an approximately 170-bp deletion of T-DNA sequence and another Ds transposition carried a 272-bp T-DNA sequence. Using thermal asymmetric interlaced PCR (TAIL-PCR), some flanking se- quences of the Ds element were amplified. Analyses of 17 Ds-flanking sequences showed that five Ds were inserted into gene regions. The Ds could transpose not only to the linked sites but also to the unlinked sites. The frequency of inter-chromosomal transposition of Ds was 33.3%.