Temporal and spatial dynamics of soil moisture are little known on karst hillslope with shallow soil in subtropical region. The objectives of this paper were (1) to investigate the temporal dynamics of soil moisture at depth of 0-10 cm under different land uses; and (2) to understand the relationship between mean and coefficient of variation (CV) of moisture contents on karst hillslope in northwest Guangxi, China. Soil moisture contents had a moderate variation (CV 17.5-30.3%) over an 8-month period and they had a significant difference among different land uses at the 0.01 level with a decreasing order: native scrubland [ abandoned cropland and sloping cropland [ economic forestland. There were higher mean and lower CV of moisture contents in rainy season than those in drought season. Mean and CV of moisture contents had a significant negative linear relationship except in abandoned cropland with higher soil and vegetation heterogeneity. This suggested that spatial variability of soil moisture within sampling sites would decrease when soils were wet and increase when soils were arid. Compared with rainy season, more soil samples may be needed and the interval for sampling should be shortened in drought season. Such information provided some insights to better understand the dynamics and variability of soil moisture at a larger scale in karst region of southwest China.

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In this study, a full-length cytosolic heat shock protein 70 complementary DNA (cDNA) of Laminaria japonica (designated as LJHsp70) was obtained by reverse transcriptase-polymerase chain reaction (RT-PCR) coupled with rapid amplification of cDNA ends. The full length of LJHsp70 cDNA was 2,918 bp, with a 5' untranslated region of 248 bp, a 3' untranslated region of 696 bp, and an open reading frame of 1,974 bp encoding a polypeptide of 657 amino acids with an estimated molecular mass of 72.03 kDa and an estimated isoelectric point of 4.97. There was highly repeated sequence of CAA in 5' untranslated region of LJHsp70. The result of phylogenetic tree of Hsp70s, the BLAST program, analysis and cytosolic Hsp70-specific motif of LJHsp70 verified that the cloned LJHsp70 belonged to cytosolic Hsp70 family. Three typical Hsp70 signature motifs were detected in LJHsp70 by InterPro analysis. Under different stress conditions, messenger RNA (mRNA) expression levels of LJHsp70 were quantified by quantitative RT-PCR. To L. japonica sporophytes kept in different temperatures for 1 h, the expression level of LJHsp70 at 30 degrees C was highest and twofold higher than that at 10 degrees C. To L. japonica sporophytes kept at 25 degrees C for different times, the mRNA expression level of LJHsp70 reached a maximum level after 7 h and then dropped progressively. The expression level of LJHsp70 at 0 or 5 per thousand salt concentration for 2 h was twofold higher than that at 30 per thousand salt concentration for 2 h. The results showed that LJHsp70 may be a kind of potential biomarker used to monitor environment conditions.

Expressed sequence tag-derived microsatellite markers (EST-SSR) were generated and characterized in Laminaria japonica using data mining from updated public EST databases and polymorphism testing. Fifty-eight of 578 ESTs (10.0%) containing various repeat motifs were used to design polymerase chain reaction (PCR) amplification primers. A total of 12 pairs of primer were generated and used in the PCR amplification. Alleles per locus ranged from two to ten (average of 5.7). The observed heterozygosities and expected heterozygosities were from 0.045 to 0.543 and from 0.056 to 0.814, respectively. All loci were in Hardy-Weinberg equilibrium and no linkage disequilibrium was detected. These robust, informative, and potentially transferable polymorphic markers appear suitable for population, genetic, parentage, and mapping studies of L. japonica.

Marine bacterium Vibrio sp. F-6, utilizing agarose as a carbon source to produce agarases, was isolated from seawater samples taken from Qingdao, China. Two agarases (AG-a and AG-b) were purified to a homogeneity from the cultural supernatant of Vibrio sp. F-6 through ammonium sulfate precipitation, Q-Sepharose FF chromatography, and Sephacryl S-100 gel filtration. Molecular weights of agarases were estimated to be 54.0 kDa (AG-a) and 34.5 kDa (AG-b) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The optimum pH values for AG-a and AG-b were about 7.0 and 9.0, respectively. AG-a was stable in the pH range of 4.0-9.0 and AG-b was stable in the pH range of 4.0-10.0. The optimum temperatures of AG-a and AG-b were 40 and 55 degrees C, respectively. AG-a was stable at temperature below 50 degrees C. AG-b was stable at temperature below 60 degrees C. Zn(2+), Mg(2+) or Ca(2+) increased AG-a activity, while Mn(2+), Cu(2+) or Ca(2+) increased AG-b activity. However, Ag(+), Hg(2+), Fe(3+), EDTA and SDS inhibited AG-a and AG-b activities. The main hydrolysates of agarose by AG-a were neoagarotetraose and neoagarohexaose. The main hydrolysates of agarose by AG-b were neoagarooctaose and neoagarohexaose. When the mixture of AG-a and AG-b were used, agarose was mainly degraded into neoagarobiose.

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