Multicellular genesis of leaf primordium was demonstrated via chimaeric transgenic plant of maize (Zea mays L.) regenerated from Type II calli.

Type-II embryonic calli were induced from immature embryos of maize (Zea mays L.) genotype YD and bombarded with beta-glucuronidase gene. Bombarded calli were proliferated on normal N6 medium for 2 weeks at 26°C in the dark and selected on N6 medium containing 1 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) and 5 mg/l phosphinothricin (PPT) but without casamino acids and proline under the same conditions for 14 days. Regeneration was carried out on hormone-free MS medium containing 5 mg/l phosphinothricin at 26°C under 3000 lux illumination. Plants over 8 cm were transplanted into soil and sprayed with 250 mg/l phosphinothricin when two new leaves appeared. Except normal transgenic plants, chimaeric transgenics also were regenerated in the present work. The expression pattern of beta-glucuronidase gene in leaves of chimaeric transgenic plant revealed that more than one cell formed leaf primordium at the initial stage, and filial cells stemed from each cell in leaf primordium arranged in a row longitudinally from leaf base to leaf apex. There was a clear boundary as a straight line between the area formed by transformed cells and the area formed by normal cells. A hypothesis was put forward that the primitive cells in leaf primordium divided in a longitudinal style, resulted in leaf elongation, then the filial cells divided transversally and synchronously toward the outside to broaden the leaf.

[Effects of Slope Position and Soil Horizon on Soil Microbial Biomass and Abundance in Karst Primary Forest of Southwest China].

To explore the effects of slope position and soil horizon on soil microbial biomass and abundance, chloroform fumigation extraction methods and real-time fluorescence-based quantitative PCR (Real-time PCR) were adopted to quantify the changes of soil microbial biomass C, N and abundance of bacteria and fungi, respectively. Soil samples were harvested from three horizons along profile, i. e., leaching horizon (A, 0-10 cm), transitional horizon (AB, 30-50 cm) and alluvial horizon (B, 70-100 cm), which were collected from the upper, middle and lower slope positions of a karst primary forest ecosystem. The results showed that slope position, soil horizon and their interaction significantly influenced the soil microbial biomass and abundance (P < 0.05). Different from A horizon, where SMBC was greater in lower than in upper slope position (P < 0.05), SMBC in AB and B horizons were highest in middle slope position. Similarly, SMBN was greater in lower than in upper slope position for A, AB and B horizons. Besides soil bacterial abundance in B horizon and fungal abundance in AB layer, the middle slope position had the highest value for all the three soil horizons (P < 0.05). Stepwise regression analysis showed that soil organic carbon, available nitrogen and pH were the key factors responsible for SMBC and SMBN variation, respectively, while the important factors responsible for the variation of bacteria abundance were available nitrogen and available phosphorus, and that for fungi abundance variation were available potassium.

[Effect of long-term fertilization on lignin accumulation in typical subtropical upland soil].

To investigate the effect of long-term fertilization on lignin accumulation and clarify its influencing factors in subtropical agricultural upland soils, alkaline CuO oxidation and gas chromatography was performed to quantify the amount of lignin and its monomers components (V, S and C). The soil samples were collected from the fertilization treatments of NPK and NPKS (NPK combined with straw) in Huanjiang County, Guangxi Province (limestone soil) and Taoyuan County, Hunan Province (red soil). The results showed that NPK had no significant effect on the lignin content (Sumvsc) of limestone soil, whereas the content in red soil significantly increased by (55 ± 1)%. For the NPKS treatment, the lignin content in limestone and red soil increased by (328 ± 4)% and (456 ± 9)%, respectively. After the same fertilization treatment, the proportion of cinnamyl (C)-type significantly increased in red soil, while a significant increase of vanillyl (V)-type monomers occurred in limestone soil, indicating that lignin degradation in agricultural soils was monomer specific. Furthermore, the acid-to-aldehyde ratios of syringyl-type [(Ac/Al)] or vanillyl-type [(Ac/Al)v] monomers tended to decrease after long-term fertilization with the higher value for limestone soil, suggesting the degree of lignin degradation in limestone was higher than that in red soil. Soil organic matter and total nitrogen were not correlated with lignin content, but were significantly correlated with the composition of VSC monomers. Meanwhile, the available nutrient content in the soil (available nitrogen, phosphorus, and potassium) was closely related to the contents and components of V, S, and C-type monomers (P<0.05). It indicated that the availability of soil nutrition should be considered as a key factor for the accumulation of lignin.

[Basidiomycetous laccase gene diversity in two subtropical forest soils].

As one of the key enzymes involved in lignin decomposition of forest litter, laccase plays an important role in the carbon cycling in forest ecosystem. By using TA cloning and sequencing, a comparative study was conducted on the basidiomycetous laccase gene diversity in the O horizon (litter layer) and A horizon (surface soil layer, 0-20 cm) in two subtropical forests (a primeval evergreen deciduous broadleaved mixed forest and an artificial masson pine forest). For the same soil horizons, the basidiomycetous laccase gene diversity and richness were higher in the primeval forest than in the masson pine forest; for the same forest ecosystems, the basidiomycetous laccase gene diversity and richness in the primeval forest were slightly higher in O horizon than in A horizon, but those in the masson pine forest were apparently lower in O horizon than in A horizon. The two forest soils had the same dominant laccase gene-containing basidiomycetous populations, and most of the populations had high similarity of amino acid sequence to Mycena sp. or Pleurotus sp. belonging to Agaricales. Comparing with the A horizon in primeval forest and the O horizon in masson pine forest, the O horizon in primeval forest and the A horizon in masson pine forest had a relatively uniform distribution of basidiomycetous populations. The nucleotide sequence similarity of basidiomycetous laccase gene between the O and A horizons in the masson pine forest was higher than that in the primeval forest. This study showed that vegetation and soil horizon had significant effects on the basidiomycetous laccase gene diversity and community structure, and the discrepancies in the substrate availability for basidiomycetes and in the soil pH induced by the vegetation and soil horizon could be the driving forces.

[Expression activity of maize Ubi-1 promoter in fertile transgenic maize plants].

The encoding sequence of gus gene from Escherichia coli was fused with maize Ubi-1 promoter and was introduced into maize genome via particle bombardment. Fertile transgenic maize plants were regenerated from bombarded type-I calluses which were derived from scutellar tissue of immature embryos based on PPT selection. Expression activity of gus gene under the control of Ubi-1 promoter was analysed using histochemical method, and the results showed that gus gene expressed in most tissues except anther. Ubi-GUS expression in pollen, egg cell and T1 immature embryos revealed that this promoter was active in early stages of plant development. Histochemically stained pollen grains of T0 plants showed a 1:1 segregation of the gus gene, which suggested that the foreign gene was inherited in Mendelian model in these plants. In addition, maize Ubi-1 promoter could reduce the copy number of foreign genes in transgenic maize plants, which might be useful in avoidance of gene silencing. T1 seeds have been harvested.