植物生理与分子生物学学报最新文献

To provide a useful piece of information for the choice of molecular markers to be used in selection of drought tolerance, mRNA differential display was used to isolate genes from a drought-tolerant maize inbred line '81565'. After drought stress, two down-regulated expression gene fragments (MD1 and MD2) and one up-regulated expression fragment (MD3) were obtained. Results of sequence and homology analysis show that MD1 has 97% similarity with matK in maize chloroplast genome, a gene encoding RNA maturase involved in group II intron splicing of RNA transcript; MD2 has 99% similarity with the gene serine/threonine phosphorylase 2C in Sporobolus stapfianus; and MD3 has 99% similarity with rice the gene encoding metacaspase, an arginine/lysine-specific cysteine protease. Based on the sequence of fragment MD2, a new member of maize PP2C gene family, ZmPP2Ca, was cloned by in silicon cloning and reverse transcription polymerase chain reaction (RT-PCR). Real-time fluorescence quantitative polymerase chain reaction (FQ-PCR) showed that expression of the gene was down-regulated in the three drought-tolerant lines ('81565', 'N87-1' and 'R09') and up-regulated in the two drought-sensitive lines ('200B' and 'ES40') under drought stress.

Wild banana species are essential natural gene pools for banana improvement. In this study, six RGAs about 500 bp were obtained from leaves of Musa acuminata, a wild banana shown to be resistant to banana Fusarium wilt race 4, by PCR amplification with degenerate primers designed according to the conserved NBS motif and serine/threonine kinase domain of plant resistance (R) genes. Among these RGAs, the deduced amino acids of WNB1 and WNB2 contain NB-ARC domain and WNB1 can be translated into polypeptide uninterrupted by stop codons. The deduced amino acids of other four RGAs (WST1, WST2, WST3 and WST4) all contain the serine/threonine kinase domain and WST3 encodes a polypeptide homologous to that of bacterial blight resistance gene Xa21 of rice. At different time after inoculation with Fusarium oxysporum f. sp. cubense (FOC) race 4, the transcript patterns of WNB1 and WST3 was enhanced, which implied that the expression of WNB1 and WST3 may be related to the resistance of banana to Fusarium wilt.

Compared to Pi-ta(-) alleles, Pi-ta(+) alleles can cause blast resistance response. In this work, Pi-ta gene in multiple rice materials, including local rice cultivars, different types of O. rufipogon and O. longistaminata was detected by molecular cloning and sequence analysis. Results indicated that Pi-ta(+) alleles were rare alleles, because in all the tested materials, only the 'Erect' type of O. rufipogon (ETOR) from Jinghong county in Yunnan province contains a Pi-ta(+) allele. Another rice blast resistance gene, Pib, confers resistance to the Japanese strain of M. grisea, was also confirmed to be functional in this type of O. rufipogon. The results of pathogen inoculation test show that ETOR is more strongly resistant to the tested blast pathogen races than other types of O. rufipogon. The resistance of ETOR may at least partially depend upon the functioning of Pi-ta and Pib gene. As O. rufipogon has the same type of genome with the cultivated rice (O. sativa), Pi-ta(+) and Pib gene in Erect type of O. rufipogon can be used to improve the tolerance of cultivated rice to blast, either by traditional hybridization or by genetic engineering.

To explore the possible regulatory role of chlorophyllase (Chlase) in chlorophyll (Chl) degradation during leaf senescence, RNAi Arabidopsis (Arabidopsis thaliana) plants were constructed to repress the expressions of AtCLH1 and/or AtCLH2. Transcript levels of AtCLH1 and/or AtCLH2 were dramatically lowered and Chlase activity was correspondingly inhibited, but the Chl degradation kinetics was not affected in the RNAi plants. Results of further analysis indicated that the Chl a/b ratio decreased in AtCLH1 RNAi lines, in comparison with the increasing Chl a/b ratio in the wide type during leaf senescence. In addition, an induced Chlase activity was consistently detected at the initial stage of senescence in all the plants examined. In contrast, transcript levels of both AtCLH1 and AtCLH2 decreased dramatically upon the initiation of senescence in both the wide-type and the RNAi plants. Interestingly, compared with the wide type, lower but still significant transcript levels of the RNAi targeted Chlase gene(s) were sustained during the whole period of dark incubation in all the three RNAi lines examined, indicating the functioning of some compensatively regulating mechanism. Based on these results, along with related reports, we conclude that Chlase might be required at the initial stage of leaf senescence, quite likely playing a role in converting Chl b to a.

Plant seed oil is the major source of many fatty acids for human nutrition, and also one of industrial feedstocks. Recent advances in understanding of the basic biochemistry of seed oil biosynthesis, coupled with cloning of the genes encoding the enzymes involved in fatty acid modification and oil accumulation, have set the stage for the metabolic engineering of oilseed crops that produce "designer" plant seed oils with the improved nutritional values for human being. In this review we provide an overview of seed oil biosynthesis/regulation and highlight the key enzymatic steps that are targets for gene manipulation. The strategies of metabolic engineering of fatty acids in oilseeds, including overexpression or suppression of genes encoding single or multi-step biosynthetic pathways and assembling the complete pathway for the synthesis of long-chain polyunsaturated fatty acids (e.g. arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid) are described in detail. The current "bottlenecks" in using common oilseeds as "bioreactors" for commercial production of high-value fatty acids are analyzed. It is also discussed that the future research focuses of oilseed metabolic engineering and the prospects in creating renewable sources and promoting the sustainable development of human society and economy.

The xylA gene, encoding xylose isomerase, was cloned as a 1342-bp BamHI/SacI fragment from the E. coli. As a selection marker, the xylA gene was fused between the enhanced CaMV 35S promoter (E35S) and terminator (35St) in pBAC413 (Fig.2). pBAC413 was constructed to prevent the expression of sbeIIb in maize. PDS1000/He was used to bombard maize calli, which were induced to form by the elite inbred lines. The selection was carried out on the media containing concentrations of xylose from 0 to 100%. The results showed that the media containing 50% to 100% D-xylose were better, but differed with the genotype of maize (Tables 1 and 2). Successful integration of xylA gene into the maize genome was confirmed by DNA dot blotting, PCR and PCR-Southern hybridization (Figs.4 to 6). A method was established in which transformed maize cells were successively screened on a medium containing xylose instead of antibiotic and herbicide for bio-safety.

When measured at a same CO(2) concentration, net photosynthetic rate is often significantly lower in long-term high CO(2)-grown plants than the ambient CO(2)-grown ones. This phenomenon is termed photosynthetic acclimation or down-regulation. Although there have been many reports and reviews, the mechanism(s) of the photosynthetic acclimation is not very clear. Combining the work of the authors' group, this paper briefly reviews the progress in studies on the mechanism(s) of the photosynthetic acclimation to elevated CO(2). It is suggested that besides the possible effects of respiration enhancement and excessive photosynthate accumulation, RuBP carboxylation limitation and RuBP regeneration limitation are probably the main factors leading to the photosynthetic acclimation.

The influence of aluminum (Al) on physiological and biological characteristics of soybean under manganese (Mn) stress was investigated. The results showed that Al suppressed the transport of Mn to shoots (Fig.2B, C), and subsequently alleviated the inhibition of shoot growth (Fig.1), decreased the chlorophyll content (Fig.4). Addition of Al diminished the increase in O(-*)(2) producing rate, the hydrogen peroxide (H(2)O(2)) content and malondialdehyde (MDA) content, and activities of superoxide dismutase (SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX) in soybean leaves caused by excessive Mn (Fig.5), and prevented the dropping of CAT activity to a low level under excessive Mn stress (Fig.6). Results of fractional analysis indicated that high levels of Al supply deduced mainly accumulation of Mn both in cell walls and organelles, but had no effect on it in soluble fractions (Fig.3).

LEAFY (LFY) gene plays an important role in determining plant flowering mainly by controlling the timing of phase transition. Constitutive under-expression of LFY in Arabidopsis resulted in the formation of a late-flowering and highly branching phenotype. In this paper, an RNAi approach was used in down-regulated LFY gene expression to delay Chinese cabbage (Brassica rapa L. ssp. pekinensis) bolting and flowering. The results show that transgenic plant has a later transition to the reproductive phase, and the transgenic plants have more branches, more leaves, but a lower height. Results of RQ-RT-PCR analysis show that LFY gene expression was greatly reduced in transgenic plants. These results suggest that inhibiting LFY gene expression by RNA interference can delay bolting in a cold-sensitive long-day (LD) condition. Late flowering of Chinese cabbage can be used as a good genetic resource for the breeding late-bolting Chinese cabbage.

Vacuolated mesophyll protoplasts of Nicotiana rustica L. were electrically fused with evacuolated protoplasts of the same genus (N. tabacum cv. 'Gexin No.1') during a 7-day space flight in the Chinese spacecraft "SZ-4". The initial cell division leading to micro-callus formation took place after landing (Fig.1). Higher plating efficiencies were observed in the flight samples than the control culture, but the frequency of plantlets regeneration reduced by about 20% of the control (Table 1). The hybrid characters were tested by chromosome counting, isozyme analysis and comparison of morphological characteristics (Figs.2-4). About 32% of the regenerates showed hybrid character. Leaf morphological modifications were found in 3 hybrids, i.e., H23, H25 and H27. After backcrossing with N. rustica, alterations in flower color and leaf shape occurred in the somatic hybrid H23 (Fig.5). These results demonstrate that the hybrids formed under microgravity condition could regenerate fertile plants.