High cell density culture of the diatom Nitzschia laevis for eicosapentaenoic acid production: fed-batch development

A fed-batch process was developed for high cell density culture of the diatom Nitzschia laevis for enhanced production of eicosapentaenoic acid (EPA). Firstly, among the various medium components, glucose (Glu) was identified as the limiting substrate while nitrate (NO₃⁻), tryptone (Tr) and yeast extract (Ye) were found to promote cell growth by enhancing specific growth rate. Therefore, these components were considered essential and were included in the feed medium for subsequent fed-batch cultivation. With the optimized ratio of NO₃⁻:Tr:Ye being 1:2.6:1.3 (by weight), the relative proportions of glucose to the nitrogen sources in the feed were investigated. The optimal ratios of Glu:NO₃⁻ for specific growth rate and EPA productivity were both determined to be 32:1 (by weight). Finally, based on the residual glucose concentration in the culture, a continuous medium feeding strategy for fed-batch fermenter cultivation was developed, with which, the maximal cell dry weight and EPA yield obtained were 22.1 g l⁻¹ and 695 mg l⁻¹, respectively, which were great improvements over those of batch cultures.     

Meiotic Chromosome Behavior in a Human Male t（8;15） Carrier

Reciprocal translocation is one of the most common structural chromosomal rearrangements in human beings; it is widely recognized to be associated with male infertility. This association is mainly based on the abnormal chromosome behavior of the translocated chromosomes and sex chromosomes during meiosis prophase I in reciprocal translocation carriers. However, the underlying mechanisms are not completely known. Here we report a reciprocal translocation carrier of t（8;15）, who is oligozoospermic due to apoptosis of primary spermatocytes and to premature germ cell desquamation from seminiferous tubules. Further analysis showed abnormal synapsis and recombination frequency in this patient, indicating a connection between chromosome behavior and apoptosis of primary spermatocytes. We also compared these observations with recently reported findings on spermatogenesis defects in reciprocal translocation carriers, and discuss the possible mechanisms underlying both common and unique phenotypes of reciprocal translocations involving different chromosomes with the aim of further understanding the regulation of human spermatogenesis.     

Coffee polyphenol caffeic acid but not chlorogenic acid increases 5'AMP-activated protein kinase and insulin-independent glucose transport in rat skeletal muscle

Chlorogenic acid is an ester of caffeic and quinic acids, and is one of the most widely consumed polyphenols because it is abundant in foods, especially coffee. We explored whether chlorogenic acid and its metabolite, caffeic acid, act directly on skeletal muscle to stimulate 5'-adenosine monophosphate-activated protein kinase (AMPK). Incubation of rat epitrochlearis muscles with Krebs buffer containing caffeic acid (≥0.1 mM, ≥30 min) but not chlorogenic acid increased the phosphorylation of AMPKα Thr(172), an essential step for kinase activation, and acetyl CoA carboxylase Ser(79), a downstream target of AMPK, in a dose- and time-dependent manner. Analysis of isoform-specific AMPK activity revealed that AMPKα2 activity increased significantly, whereas AMPKα1 activity did not change. This enzyme activation was associated with a reduction in phosphocreatine content and an increased rate of 3-O-methyl-d-glucose transport activity in the absence of insulin. These results suggest that caffeic acid but not chlorogenic acid acutely stimulates skeletal muscle AMPK activity and insulin-independent glucose transport with a reduction of the intracellular energy status.     

The growth characteristics and yield potential of rice (Oryza sativa) under non‐flooded irrigation in arid region

The objectives of this field experiment were to study the growth characteristics and yield potential of rice plants under non‐flooded irrigation in arid area. Non‐flooded treatments included drip irrigation with plastic mulching treatments (DIs), furrow irrigation with plastic mulching treatment (FIM) and furrow irrigation with non‐mulching treatment (FIN). Conventional flooded cultivation (F) was check treatment (CK). The four drip irrigation treatments differed in the amount of water applied before and after panicle initiation. Root length density, leaf dry weight, shoot dry weight and root activity were generally higher in the non‐flood‐irrigated treatments (especially the drip‐irrigated treatments) than in the flood‐irrigated treatment at mid‐tillering. However, the growth and development of rice plants were limited after jointing in the non‐flooded irrigation treatments. Increasing the root/shoot ratio and root length density in the 20–40 cm depth and decreasing specific root length at 0–20 cm soil layer were important mechanisms for helping the rice plants to adapt to the non‐flooded environmental stresses. Finally, the grain yield in the non‐flooded irrigation treatments was lower than that in the F treatment. These low yields were mainly attributed to the low root length density at 0–20 cm depth and root activity. Generally speaking, the restricted degrees in the DIs were smaller than that in the FIM and FIN treatments. Among the DIs, both the highest grain yield (8223–8900 kg ha^?1) and the highest water use efficiency (WUE) (0.63) were observed when the soil water content was kept at ?30 kPa before panicle initiation and at ?15 kPa after panicle initiation (referred to as the DI2 treatment). The yield in the DI2 treatment was not significantly different than that in the flood‐irrigated treatment. However, WUE was 2.5 times higher in the DI2 treatment than in the F treatment. These results suggest that drip irrigation technology can be considered as a better water‐saving cultivation of rice plants in arid region.     

Pollen size strongly correlates with stigma depth among Pedicularis species

Darwin proposed that pollen size should be positively correlated with stigma depth rather than style length among species given that pollen tubes first enter the stigma autotrophically, then grow through the style heterotrophically. However, studies often show a positive relationship between pollen size and style length.Five floral traits were observed to be correlated among42 bumblebee-pollinated Pedicularis species(Orobanchaceae) in which stigmas are distinct from styles. The phylogenetic independent contrast analysis revealed that pollen grain volume was more strongly correlated with stigma depth than with style length, consistent with Darwin's functional hypothesis between pollen size and stigma depth.     

A maize ADP‐ribosylation factor ZmArf2 increases organ and seed size by promoting cell expansion in Arabidopsis

ADP‐ribosylation factors (ARFs) are small GTP‐binding proteins that regulate a wide variety of cell functions. Previously, we isolated a new ARF, ZmArf2, from maize (Zea mays). Sequence and expression characteristics indicated that ZmArf2 might play a critical role in the early stages of endosperm development. In this study, we investigated ZmArf2 function by analysis of its GTP‐binding activity and subcellular localization. We also over‐expressed ZmArf2 in Arabidopsis and measured organ and cell size and counted cell numbers. The expression levels of five organ size‐associated genes were also determined in 35S::ZmArf2 transgenic and wild‐type plants. Results showed that the recombinant ZmArf2 protein purified from Escherichia coli exhibited GTP‐binding activity. Subcellular localization revealed that ZmArf2 was localized in the cytoplasm and plasma membrane. ZmArf2 over‐expression in Arabidopsis showed that 35S::ZmArf2 transgenic plants were taller and had larger leaves and seeds compared to wild‐type plants, which resulted from cell expansions, not an increase in cell numbers. In addition, three cell expansion‐related genes, AtEXP3, AtEXP5 and AtEXP10, were upregulated in 35S::ZmArf2 transgenic lines, while the expression levels of AtGIF1 and AtGRF5, were unchanged. Collectively, our studies suggest that ZmArf2 has an active GTP‐binding function, and plays a crucial role in growth and development in Arabidopsis through cell expansion mediated by cell expansion genes.     

Soil carbon dynamics in a Pinus massoniana plantation following clear-cutting and slash removal

Aims Slash removal is a common practice to prepare recently harvested sites for replanting. However, little is known about its impact on soil carbon (C) dynamics in subtropical plantations. This study evaluates the effects of burning versus manual slash removal site preparation treatments on soil organic carbon (SOC), soil respiration and soil microbial community structure in a Pinus massoniana plantation in southern China.Methods Three areas within a mature P. massoniana plantation were clearcut. Two months following harvesting, slash on one-half of each area was burned (BURN), whereas slash was manually removed (MANR) on the other portion. Slash removal treatments were also compared with adjacent uncut plantation areas (UNCUT). Soil samples, and soil respiration measurements were used to characterize soil properties and microbial communities following slash removal treatments. Important findings Mean soil respiration rates from the MANR and BURN treatments were 26% and 17% lower, respectively, than the UNCUT treatment over 1 year. The MANR and BURN treatment resulted in soils with 27% and 9% reduction in total phospholipid fatty acids (PLFAs) and 18% and 10% reduction in bacterial PLFAs, respectively, compared with the UNCUT treatment. However, no significant differences existed between slash removal treatments with respect to soil chemical properties, SOC chemical compositions, soil respiration and microbial communities; although PLFA patterns were notably different for the burned plots. Most factors affecting C dynamics and microbial communities were not sensitive to the differences imparted to the ecosystem due to manual slash removal or burning. Our results suggested that low-intensity burning after clear-cutting might have no significant effect on soil C pool and its dynamics compared with manual slash removal in subtropical plantations.