Expression Profile Matrix of Arabidopsis Transcription Factor Genes Suggests Their Putative Functions in Response to Environmental Stresses

Numerous studies have shown that transcription factors are important in regulating plant responses to environmental stress. However, specific functions for most of the genes encoding transcription factors are unclear. In this study, we used mRNA profiles generated from microarray experiments to deduce the functions of genes encoding known and putative Arabidopsis transcription factors. The mRNA levels of 402 distinct transcription factor genes were examined at different developmental stages and under various stress conditions. Transcription factors potentially controlling downstream gene expression in stress signal transduction pathways were identified by observed activation and repression of the genes after certain stress treatments. The mRNA levels of a number of previously characterized transcription factor genes were changed significantly in connection with other regulatory pathways, suggesting their multifunctional nature. The expression of 74 transcription factor genes responsive to bacterial pathogen infection was reduced or abolished in mutants that have defects in salicylic acid, jasmonic acid, or ethylene signaling. This observation indicates that the regulation of these genes is mediated at least partly by these plant hormones and suggests that the transcription factor genes are involved in the regulation of additional downstream responses mediated by these hormones. Among the 43 transcription factor genes that are induced during senescence, 28 of them also are induced by stress treatment, suggesting extensive overlap responses to these stresses. Statistical analysis of the promoter regions of the genes responsive to cold stress indicated unambiguous enrichment of known conserved transcription factor binding sites for the responses. A highly conserved novel promoter motif was identified in genes responding to a broad set of pathogen infection treatments. This observation strongly suggests that the corresponding transcription factors play general and crucial roles in the coordinated regulation of these specific regulons. Although further validation is needed, these correlative results provide a vast amount of information that can guide hypothesis-driven research to elucidate the molecular mechanisms involved in transcriptional regulation and signaling networks in plants

Concurrent local dynamics in elementary cellular automata

Typescript (photocopy).Cellular Automata provide a class of formal abstractions of natural systems which have simple components but complex overall behaviors. This study investigated the dynamics of cellular automata from a local perspective and concentrated on some generic local behaviors rather than on the changes of entire, infinite configurations of cellular automata. The concept of the local system and the state of the local system was first established. A cellular Automaton was viewed as a collection of an infinite number of local systems undergoing concurrent state-transitions. According to whether or not "influence" can pass through a local system, two different type of states was identified, namely, the permeable state and the impermeable state. The existence of stable local attractor within impermeable states distinguishes the periodic dynamical phase from chaotic and complex (emergent) dynamical phase, and the existence of quasi-stable attractor further separates complex behavior form chaos. The quasi-stable attractors are those attractors whose stabilities are not Turing-decidable. These type of attractors set up a sufficient and necessary condition upon which order can be generated from chaos. This understanding potentially opens up numerous applications, and also leads to a computational worldview that could unify science in a different way

A unified theory of spatial patterns for sessile biological individuals and structures

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Bibliography: leaves 37-38.Not availabl

Effects of elevated CO2 on the red seaweed Gracilaria lemaneiformis (Gigartinales, Rhodophyta) grown at different irradiance levels

The red seaweed Gracilaria lenzaneiformis (Bory) Weber-van Bosse (Gigartinales, Rhodophyta) from Nanao Island, Shantou, China, was cultured at 370 and 700 mu l l(-1) CO2 in aeration and at intermediate (160 mu mol photons m(-2) s(-1)) and low (30 mu mol photons m(-2) s(-1)) irradiance levels in order to examine the influences of the elevated atmospheric CO2 concentrations on growth, photosynthetic performance and some biochemical components in this commercially important species. Relative growth rate (RGR) was significantly higher in G. lemaneiformis thalli grown using CO2-enriched air with respect to nonenriched air when the algae were subjected to intermediate irradiance. However, RGR was similar between these two CO2 treatments when the algae were grown under the low-irradiance condition. Extra CO, in the culture decreased phycobiliprotein (PB, including phycoerythrin, PE, and phycocyanin, PC) contents of G. lemaneiformis thalli at the higher growth irradiance. However, chlorophyll a (Chl a) and soluble protein contents were unchanged by the CO2 levels in culture. Both PB and Chl a contents were higher in G. lemaneiformis thalli grown at the lower irradiance than at the higher irradiance, regardless of the CO2 levels in culture. The parameters for photosynthetic responses to irradiance and inorganic carbon were mostly not altered with the increase Of CO2 concentrations in culture. However, light-saturated photosynthetic rates (P-max) and apparent carboxylating efficiencies (ACE), expressed per unit Chl a, were significantly higher in algae grown at the intermediate irradiance compared to the low irradiance. Photosynthetic rate was reduced by an increase in pH of seawater from 8.2 to 9.1, and it was also strongly inhibited by the external carbonic anhydrase inhibitor acetazolamide (AZ) in G. lemaneiformis thalli grown at each CO2 and irradiance condition. Moreover, pH compensation points were not affected by the growth conditions. These results suggested that G. lemaneiformis under both growth conditions had a similar capacity of the photosynthetic utilization of external HCO3- pool in seawater. However, ACE decreased in G. lemaneiformis thalli grown at the low irradiance with respect to the higher irradiance implied that the transport of Ci towards Rubisco within the cell was weakened. Taken together, the data showed that an increase of CO2 was less effective on G. lemaneiformis than the irradiance levels. We concluded that CO2 affected photosynthesis and growth performance when light was not the limiting factor.National Natural Science Foundation of China [30670396, 90411018]; Chinese Ministry of Education [207080]; Chinese 973 Project [2009CB21207]; Guangdong Natural Science Foundation [2006B20601005, 2007A02600003

Acquisition of inorganic carbon by Endarachne binghamiae (Scytosiphonales, Phaeophyceae)

Photosynthetic acquisition of inorganic carbon was studied in the brown seaweed Endarachne binghamiae J. Agardh. Photosynthesis was saturated at 245 mu mol photons m-2 s-1 and photoinhibition did not occur at an irradiance as high as 750 mu mol photons m-2 s-1. The dependence of O2 evolution on inorganic carbon (Ci) concentration demonstrated that the normal Ci composition in natural seawater was not saturating for irradiance-saturated photosynthesis. Three lines of evidence demonstrated that E. binghamiae was able to acquire [image omitted] as a source of Ci for photosynthesis: (i) the high value of photosynthetic conductance for CO2 (220.6 mu m s-1); (ii) the high pH compensation point of 9.7; and (iii) the measured photosynthetic rates being in excess of the theoretical maximum rates supported solely by the CO2 supply from the spontaneous dehydration of [image omitted] in the bulk seawater. In order to establish the mechanism of Ci acquisition, specific inhibitors and a proton buffer were applied to examine their inhibitory effects on photosynthesis. No inhibitory effects were found for the proton buffer tris(hydroxymethyl)aminomethane and the anion exchanger inhibitor, 4,4'-diisothiocyano-stilbene-2,2'-disulphonate. By contrast, photosynthetic O2 evolution in natural seawater was significantly depressed by the extracellular carbonic anhydrase (CA) activity inhibitor, acetazolamide, and the plasma membrane P-type H+-ATPase inhibitor, vanadate. These results suggested that carbon acquisition from the natural seawater was mostly through the external CA-mediated [image omitted] dehydration mechanism, and that P-type H+-ATPase (proton pump) in the plasma membrane simultaneously functioned in photosynthesis of E. binghamiae. Additional experiments on the O2 exchange versus pH value relationship indicated that, in contrast to photosynthesis, dark respiration of E. binghamiae was insensitive to the change of pH in the seawater, which resulted in a decreasing instantaneous balance between net carbon gain and respiratory carbon loss at high pH values in seawater.Chinese 973 Projects [2009CB421207]; National Natural Science Foundation of China [30970450, 30670396]; Chinese 863 Projects [2006AA10A416]; Guangdong Natural Science Foundation [2007A032600003

Photosynthetic acclimation to different light levels in the brown marine macroalga, Hizikia fusiformis (Sargassaceae, Phaeophyta)

Hizikia fusiformis thalli experience dynamic incident light conditions during the period of growth. The present study was designed to examine how changing photon irradiance affects the photosynthesis both in the short and long terms by culturing H. fusiformis under three different light levels: 35 mu mol photons m(-2) s(-1) (low light, LL), 85 mu mol photons m(-2) s(-1) (intermediate light, IL), and 165 mu mol photons m(-2) s(-1) (high light, HL). A similar relative growth rate was observed between IL- and HL-grown algae, but the growth rate was significantly reduced in LL-grown algae. The photosynthetic rates (P (n)) measured at their respective growth light levels were found to be lowest in the thalli grown at LL and highest at HL. However, LL-grown algae exhibited much higher P (n) in comparison with IL- and the HL-grown thalli at the same measuring photosynthetic photon flux density, indicating the photosynthetic acclimation to low growth light in H. fusiformis. The photosynthesis-light curves showed that LL-grown algae had a highest light-saturating maximum P (n) (P (max)) in comparison with IL- or HL-grown algae when the photosynthetic rates were expressed on the biomass basis. However, P (max) was highest in HL-grown algae compared to IL- or LL-grown algae when the rates were normalized to chlorophyll a. The photosynthesis-inorganic carbon (Ci) response curves were also significantly affected by the growth light conditions. The highest value of apparent photosynthetic conductance occurred in LL-grown algae while the lowest value in HL-grown algae. Additionally, the activity of external carbonic anhydrase (CA) tended to increase while the total CA activity inclined to decrease in H. fusiformis thalli when the growth light level altered from 35 to 165 mu mol photons per square meter per second. The external CA inhibitors showed a higher inhibition in HL-grown algae compared with LL-grown algae. It was proposed that photosynthetic acclimation to low light condition in H. fusiformis was achieved through an increase in the number of reaction centers and increased capacities of electron transport and of Ci transport within cells. The ability of photosynthetic acclimation to low light confers H. fusiformis thalli to overcome the environmental low light condition as a result of the attenuation of seawater or self-shading through enhancing its photosynthetic performance and carbon assimilation necessary for growth.Chinese 973 Projects [2009CB421207]; National Natural Science Foundation of China [30670396]; Chinese 863 Projects [2006AA10A416]; Guangdong Natural Science Foundation [2007A032600003

Spatial distribution of perfluoroalkyl acids in the Pearl River of Southern China

An intensive campaign was conducted in September 2012 to collect surface water samples along the tributaries of the Pearl River in southern China. Thirteen perfluoroalkyl acids (PFAAs), including perfluorocarboxylates (PFCAs, C4-C11) and perfluorosulfonates (PFSAs, C4, C6-C8, and C10), were determined using high-performance liquid chromatography/negative electrospray ionization-tandem mass spectrometry (HPLC/(-)ESI-MS/MS). The concentrations of total PFAAs (Sigma PFAAs) ranged from 3.0 to 52 ng L-1, with an average of 19 12 ng L-1. The highest concentrations of Sigma PFAAs were detected in the surface water of the Dong Jiang tributary (17-52 ng L-1), followed by the main stream (13-26 ng L-1) and the Sha Wan stream (3.0-4.5 ng L-1). Perfluorooctanoate (PFOA), perfluorobutane sulfonate (PFBS), and perfluorooctane sulfonate (PFOS) were the three most abundant PFAAs and on average accounted for 20%, 24%, and 19% of EPFAAs, respectively. PFBS was the most abundant PFAA in the Dong Jiang tributary, and PFOA was the highest PFAA in the samples from the main stream of the Pearl River. A correlation was found between PFBS and PFOA, which suggests that both of these PFAAs originate from common source(s) in the region. Nevertheless, the slope of PFBS/PFOA was different in the different tributaries sampled, which indicates a spatial difference in the source profiles of the PFAAs. (C) 2013 Elsevier Ltd. All rights reserved.An intensive campaign was conducted in September 2012 to collect surface water samples along the tributaries of the Pearl River in southern China. Thirteen perfluoroalkyl acids (PFAAs), including perfluorocarboxylates (PFCAs, C4-C11) and perfluorosulfonates (PFSAs, C4, C6-C8, and C10), were determined using high-performance liquid chromatography/negative electrospray ionization-tandem mass spectrometry (HPLC/(-)ESI-MS/MS). The concentrations of total PFAAs (Sigma PFAAs) ranged from 3.0 to 52 ng L-1, with an average of 19 12 ng L-1. The highest concentrations of Sigma PFAAs were detected in the surface water of the Dong Jiang tributary (17-52 ng L-1), followed by the main stream (13-26 ng L-1) and the Sha Wan stream (3.0-4.5 ng L-1). Perfluorooctanoate (PFOA), perfluorobutane sulfonate (PFBS), and perfluorooctane sulfonate (PFOS) were the three most abundant PFAAs and on average accounted for 20%, 24%, and 19% of EPFAAs, respectively. PFBS was the most abundant PFAA in the Dong Jiang tributary, and PFOA was the highest PFAA in the samples from the main stream of the Pearl River. A correlation was found between PFBS and PFOA, which suggests that both of these PFAAs originate from common source(s) in the region. Nevertheless, the slope of PFBS/PFOA was different in the different tributaries sampled, which indicates a spatial difference in the source profiles of the PFAAs. (C) 2013 Elsevier Ltd. All rights reserved