Acta Agronomica Sinica最新文献

Lysophosphatidic acid acyltransferase (LPAT) is one of the key enzymes in biosynthesis pathway of triacylglycerol (TAG) in plant. A full-length cDNA library of peanut (Arachis hypogaea L.) was constructed from seed by means of a large number of sequences of expressed sequence tag (EST) and gene functional annotation. A lysophosphatidic acid acyltransferase gene, designated AhLPAT, and its genomic DNA sequence was isolated from peanut. The sequence of AhLPAT cDNA was 1753 bp, and its genomic sequence was 5331 bp. Bioinformatic analysis showed that AhLPAT was composed of 11 exons and 10 introns with typical GT-AG sequence at the splice site. A peptide of 387 amino acid residues was deduced from AhLPAT, with molecular weight of 43.2 kD and isoelectric point (pI) of 9.42. Conserved domain prediction indicated that AhLPAT comprised a typical conserved acyltransferase domain and a conserved lysophospholipid acyltransferase domain. The deduced amino acid had a high sequence similarity with the LPAT proteins from other species. Similarities for amino acid sequence of LPAT protein between peanut and Tropaeolum majus, Brassica napus, Crambe hispanica subsp. abyssinica, Ricinus communis, and Arabidopsis thaliana were 90%, 89%, 89%, 88%, and 87%, respectively. The phylogenetic tree suggested that AhLPAT and AtLPAT2 derived from A. thaliana were grouped into the same class, and both of them were endoplasmic reticulum type LPATs. The result of quantitative RT-PCR assay indicated that AhLPAT was ubiquitously expressed in root, stem, leaf, flower, gynophore, and seed of peanut with the highest level in gynophore and seed. The peak expression was in the period of 50–60 d after flowering. Correlation between AhLPAT expression and oil accumulation was significant (r = 0.63, P < 0.05). These results suggest that AhLPAT plays an important role in peanut TAG biosynthesis.

Root hair is an important organ for uptaking nutrients and water in plant. A rice (Oryza sativa L.) mutant, ossrh3, with short root hairs was isolated from a T-DNA insertion mutant library of rice on Zhonghua 11 background. The elongation of root hairs in the mutant was severely impaired. Beside, some other traits were also affected, such as plant height, primary root length, lateral root length, and number of lateral roots. Genetic analysis indicated that the mutated phenotype was controlled by a single recessive nuclear gene. An F₂ population was developed by crossing the mutant ossrh3 with an indica cultivar, Kasalath, to map the gene. Using simple sequence repeat (SSR) markers and newly designed sequence-tagged site (STS) markers, the target gene, OsSRH3, was located to a 37.7 kb region between markers S38978 and S39016 on chromosome 1. This marker interval contained 8 predicted genes.

The wild species in genus Oryza are important resources of genes resistant to brown planthopper (Nilaparvata lugens, BPH). The objective of this study was to identify quantitative trait loci (QTLs) in Dongxiang wild rice (O. rufipogon Griff.). A BC₁F₅ population and a BC₃F₃ population were developed for QTL mapping from the cross between Dongxiang wild rice and an indica rice cultivar, Xieqingzao B (O. sativa L. subsp. indica) as the recurrent parent. The BC₁F₅ population was infested with BPH collected from paddy fields. Two QTLs were identified, of which qBph2 was located in the interval of RM29-RG157 on chromosome 2 and qBph7 in the interval of RM11-RM234 on chromosome 7. The alleles from Dongxiang wild rice on qBph2 and qBph7, which explained 21.8% and 67.1% of the phenotypic variations, respectively, and reduced seedling mortality by 22.2% and 43.7%. These QTLs were validated using the BC₃F₃ population infested by BPH biotypes I, II, and III. This result shows that qBph2 confers resistance to biotypes I and II, and qBph7 confers resistance to biotypes I and III. Both QTLs show a great potential for improving BPH resistance in rice cultivars.

The objective of this study was to understand the genetic and allelomorphic relationships among different soybean (Glycine max L. Merr.) cultivars with resistance to Soybean mosaic virus (SMV). Twelve resistant (R) soybean cultivars were crossed with a susceptible (S) cultivar (Nannong 1138-2, NY30, NY185, 86-4, or 8101) to determine the inheritance of resistance to SMV strain SC4 or SC8, which were predominant in the Huang-Huai-Hai Rivers Region and Yangtze Valley in China. The R parents were also crossed with each other for allelic analysis of resistance genes from different sources. The results indicated that Ji LD42, Xudou 1, and Yuejin 4 and Qihuang 1, Zhongzuo 229, and NY58 carried a dominant resistance gene for SMV strains SC4 and SC8, respectively, whereas Kefeng 1, PI 96983, Jinda 74, Fendou 56, Dabaima, and Qihuang 22 carried single dominant resistance gene for both SC4 and SC8. The allelism test of the resistance genes to SC4 showed that the resistance genes between Dabaima and Fendou 56, Kefeng 1, and Qihuang 1, between Ji LD42 and Fendou 56, and between Jinda 74 and Zhongzuo 229 were not at the same loci. The study of resistance of F₂ plants and F_2:3 families to SC8 indicated that the single dominant resistance genes in Jinda 74 and Fendou 56 shared a common locus or two closely loci. The resistance genes between Qihuang 1 and Kefeng 1 and between Dabaima and Fendou 56 were not at the same locus for SC8. These results are useful to understand the genetic and allelomorphic relationships among various sources of resistance.

Overexpression of phosphoenolpyruvate carboxylase (PEPC) gene in transgenic rice (Oryza sativa L.) may alleviate inhibition on photosynthesis under drought stress condition. In the present research, photosynthetic light curve, chlorophyll α fluorescence parameters, pigment content, and reactive oxygen metabolism were studied in 2 PEPC transgenic rice lines under drought stress at flowering stage. The results showed that under drought stress, especially severely drought stress, net photosynthetic rate decreased dramatically under high photosynthetic active radiation (PAR) in untransformed wild type rice, while maintained unchanging in the PEPC transgenic lines under high PAR higher than 1200 μmol m⁻² s⁻¹. The photochemistry activities (F_v/F_m, ϕ_PSII, and q_P) decreased slightly under drought stress in both PEPC transgenic lines. These results indicated that PEPC enhanced the photoinhibition tolerance of rice under drought stress. The increased zeaxanthin content in leaves of the PEPC transgenic rice lines dispersed more light energy as heat under drought stress, thus decreased the producing rate in photosystem II. At the same time, the activities of superoxide dismutase, peroxidase, and catalase were higher in the PEPC transgenic rice plants than the untransformed wild type under drought stress. These enzymes could effectively diminish the reactive oxygen species and reduce the membrane lipid peroxidation.

Population improvement is a basis of germplasm enhancement and developing inbred lines in maize (Zea mays L.). For evaluating the combing abilities of Yuzong 5 developed populations derived from 5 cycles of recurrent selection, 30 testcrossing combinations were made using Huangzao 4, Dan 340, Zhongzong 5, Qi 319, Ye 478, and Mo17 as the female parents in 2 locations under the NCII design. The yield per plant of testcrossing combinations was enhanced by 3.57% per cycle, showing a remarkable effect of recurrent selection. Both half-sib recurrent selection (HS-RS) and half-sib reciprocal recurrent selection (HS-RRS) were effective for improving the general combining ability (GCA) of kernel yield and the GCA was improved in each cycle of the populations. After 3 cycles of improvement in Yuzong 5 by HS-RS, the GCA significantly increased from (11.63 of C₀ to 5.57 of C₃ population (P < 0.01). After 1 cycle of improvement by HS-RRS, the GCA increased from 5.57 of C₃ to 9.75 of C₄ population. The specific combining ability (SCA) of improved Yuzong 5 × Huangzao 4 was enhanced, which indicated an approaching Reid × SiPT heterotic pattern during Yuzong 5 improvement cycle by cycle.

Vitamin E is an essential nutrient that must be acquired regularly from dietary sources. It is a group of compounds consisting of tocotrienols and tocopherols. The structure of tocotrienols differs from that of tocopherols by the presence of 3 trans-double bonds in the hydrocarbon chain. In this study, a reverse-phase (RP) HPLC method was used to simultaneously measure the contents of either tocopherols or tocotrienols in brown rice, and to compare these parameters among 18 indica and 16 japonica rice (Oryza sativa L.) varieties. The results showed that the proportion of these vitamin E isomers differed substantially between indica and japonica rice varieties. The mean contents of vitamin E and total tocopherol were significantly higher (P < 0.01) in japonica rice than in indica rice, while the total tocotrienol content showed no difference between indica and japonica rice. The principal isomer composition of vitamin E was also different between the 2 subspecies. For example, γ-tocotrienol was the predominant component in indica rice, while the most abundant isomer was α-tocopherol in japonica rice. The ratio of total tocotrienols to tocopherols was also significantly higher (P < 0.01) in indica (1.61) than in japonica rice (0.95). Pearson's correlation analysis demonstrated that the content of α-tocopherol was positively correlated to that of α-tocotrienol in rice. The same relationship was observed for γ-tocopherol and γ-tocotrienol, but there was a negative correlation between α- and γ-isomers. Taken together, the results provide valuable information for studying the vitamin E metabolism or nutritional improvement in rice.

Fiber mutants are important materials in genetic and functional research in cotton (Gossypium hirsutum L.). A linted-fuzzless fiber mutant, designated CM mutant, was found in transgenic cotton by Agrobacterium-mediated transformation method. The pure line of this mutant was obtained in T₃ generation. PCR analysis showed that the mutated trait had no relationship with T-DNA insertion; however, point mutation during tissue culture was deduced to be responsible for the mutated trait. Analyses of inheritance and allelic tests were conducted by crossing CM mutant with TM-1, Junhai 1, and a series of fiber developmental mutants such as XinFLM, N1N1, n2n2, and T586 with linted-fuzzless fiber and XinWX, XZ142WX, SL-7-1, and MD17 with lintless-fuzzless fiber, respectively. Among the above 10 combinations, the F₁ plants were fuzzless, and all the F₂ generations of CM × TM-1 and CM × Junhai 1 showed the segregation ratio of 3:1 of linted-fuzzless to linted-fuzzed phenotypes. Based on the genetic analysis, we indicated that there was one dominantly different locus between the mutant and TM-1 or Junhai 1. Allelic tests and gene mapping showed that the fuzzless gene of the mutant was allelic to N1, dominantly controlling naked-seed trait. The scanning electron microscopy observation was conducted to show the development of fiber cell initials in CM mutant during early developmental stages (0–3 d post anthesis). Like N1N1 mutant, CM mutant delayed fiber cell formation and elongation under the control of mutated gene. Compared to N1N1, CM mutant exhibited significant higher lint percentage of CM and significant lower 100-seed weight. The mutated gene in CM is speculated to be one of the multiple alleles of dominant naked-seed N1 gene.

Introgression lines are important genetic materials for genetics study and breeding. Development of those lines involves cross and backcross processes between recipient and donor parents. The population size of BC₁F₁ is a critical parameter for fully covering donor genome and successfully obtaining desired introgression lines. However, the minimum sufficient number of BC₁F₁ plants is unknown for each species and cannot be obtained experimentally. A computer program was developed by simulating the recombination process during meiosis to define the ideal BC₁F₁ population size. The reliability of the program was confirmed by mathematics and experimental data. Three factors including linkage group number, linkage group length, and gene density were analyzed, and all of them had positive relation with the size of BC₁F₁ population. The population size increased from 6.06 to 9.49 when the linkage number increased from 5 to 40. The population size was 7.14 when the linkage group length was 80 cM, while it became 8.64 when the length was 200 cM. The population size was 7.65 with the density of 20 cM per gene and 8.22 with 10 cM per gene. The BC₁F₁ population sizes of rice (Oryza sativa L.), wheat (Triticum aestivum L.), maize (Zea mays L.), and soybean (Glycine max L. Merr.) were predicted to be 12, 13, 14–15, and 13, respectively, by the program with 95% confidential level.

Longjiang 925 is a flue-cured tobacco variety with high resistance to Tobacco mosaic virus (TMV). In this study, the cDNA extracted from the TMV-inoculated leaves of Longjiang 925 was amplified with 240 pairs of primers. Approximately 9500 gene transcript fragments were obtained, in which 12 inducible expressed gene fragments were selected by cloning and sequencing. The inducible fragments functions involved in the nucleic acid metabolism, protein synthesis and modulation, energy metabolism, stress responding, intracellular transport, and metabolism of carbohydrates. The function of a differentially expressed gene sequence, TIF2, was validated using real-time PCR with the samples collected at 0, 12, 24, 48, and 72 h post inoculation. The result indicated that TIF2 was related to TMV-resistance. Both 5′- and 3′-rapid amplification of cDNA ends (RACE) were preformed using TIF2 sequence, and the full-length cDNA sequence was 875 bp in length, containing a conjecturable coding region from 101 bp to 613 bp and encoding 170 amino acids. Analyses of Blastn and Blastp showed that this gene was probably a novel gene related to TMV resistance in tobacco.