Contents Introduction 295 Evolution of the Plant Vascular System 295 Phloem Development & Differentiation 300 Molecular Mechanisms Underlying Xylem Cell Differentiation 307 Spatial & Temporal Regulation of Vascular Patterning 311 Secondary Vascular Development 318 Physical and Physiological Constraints on Phloem Transport Function 321 Physical & Physiological Constraints on Xylem Function 328 Long‐distance Signaling Through the Phloem 339 Root‐to‐shoot Signaling 347 Vascular Transport of Microelement Minerals 351 Systemic Signaling: Pathogen Resistance 356 Future Perspectives 361 Acknowledgements 362 References 362 Abstract [ William J. Lucas (Corresponding author)] The emergence of the tracheophyte‐based vascular system of land plants had major impacts on the evolution of terrestrial biology, in general, through its role in facilitating the development of plants with increased stature, photosynthetic output, and ability to colonize a greatly expanded range of environmental habitats. Recently, considerable progress has been made in terms of our understanding of the developmental and physiological programs involved in the formation and function of the plant vascular system. In this review, we first examine the evolutionary events that gave rise to the tracheophytes, followed by analysis of the genetic and hormonal networks that cooperate to orchestrate vascular development in the gymnosperms and angiosperms. The two essential functions performed by the vascular system, namely the delivery of resources (water, essential mineral nutrients, sugars and amino acids) to the various plant organs and provision of mechanical support are next discussed. Here, we focus on critical questions relating to structural and physiological properties controlling the delivery of material through the xylem and phloem. Recent discoveries into the role of the vascular system as an effective long‐distance communication system are next assessed in terms of the coordination of developmental, physiological and defense‐related processes, at the whole‐plant level. A concerted effort has been made to integrate all these new findings into a comprehensive picture of the state‐of‐the‐art in the area of plant vascular biology. Finally, areas important for future research are highlighted in terms of their likely contribution both to basic knowledge and applications to primary industry.
Twelve aldehyde dehydrogenase (ALDH) genes have been identified in humans. These genes, located on different chromosomes, encode a group of enzymes which oxidizes varieties of aliphatic and aromatic aldehydes. Metabolic disorders and clinical problems associated with mutations of ALDH1, ALDH2, ALDH4, ALDH10 and succinic semialdehyde (SSDH) genes have been emerged. Comparison of the human ALDHs indicates a wide range of divergency (Ͼ 80ϪϽ 15% identity at the protein sequence level) among them. However, several protein regions, some of which are implicated in functional activities, are conserved in the family members.The phylogenic tree constructed of 56 ALDH sequences of humans, animals, fungi, protozoa and eubacteria, suggests that the present-day human ALDH genes were derived from four ancestral genes that existed prior to the divergence of Eubacteria and Eukaryotes. The neighbor-joining tree derived from 12 human ALDHs and antiquitin indicates that diversification within the ALDH1/2/5/6 gene cluster occurred during the Neoproterozoic period (about 800 million years ago). Duplication in the ALDH 3/10/7/8 gene cluster occurred in Phanerozoic period (about 300 million years ago). Separations of ALDH3/ALDH10 and that of ALDH7/ALDH8 had occurred during the period of appearance and radiation of mammalian species.Keywords : gene family ; genomic organization; genetic disease; genetic variant; detoxification; evolution ; phylogenetic tree. This paper reviews the functional and structural diversity and Aldehyde dehydrogenases [aldehyde: NAD(P) ϩ oxidoreductase] are a group of enzymes catalyzing the conversion of alde-evolution of the human ALDH gene family.There is no uniform nomenclature system for human and hydes to the corresponding acids by means of an NAD(P) ϩ -dependent virtually irreversible reaction. ALDHs are widely dis-animal ALDH genes and enzymes. Therefore, commonly used abbreviated human gene symbols (GBD symbols) are used for tributed from bacteria to humans.Mammalian ALDH activity was first observed in ox liver genes (in italic) and enzymes (in non-italic) in the present review. GenBank identification numbers are also given. nearly 50 years ago  and thereafter several types of ALDH were distinguished based on their physico-chemical characteristics, enzymological properties, subcellular localization, and tissue distribution [2Ϫ4]. Two ALDH genes were cloned and char-Members of ALDH families acterized in 1985 . At the present time, ten non-allelic genes Twelve known human ALDH genes and corresponding enhave been identified in the human ALDH family. In addition, zymes are listed in Proteins (enzyme subunits) encoded by these genes consist probably exist in other mammals. Protein sequences, genes and/ of about 500 amino acid residues. Catalytically active forms of or cDNAs for more than 50 animals, fungi, and bacterial ALDHs the enzymes are homodimers (ALDH3, ALDH4), homotetrahave been reported. mers (ALDH1, ALDH2, ALDH9, MMSDD) or unknown.
Mesenchymal stem cells (MSC) derived from bone marrow can potentially reduce the acute inflammatory response in spinal cord injury (SCI) and thus promote functional recovery. However, the precise mechanisms through which transplanted MSC attenuate inflammation after SCI are still unclear. The present study was designed to investigate the effects of MSC transplantation with a special focus on their effect on macrophage activation after SCI. Rats were subjected to T9-T10 SCI by contusion, then treated 3 days later with transplantation of 1.0 · 10 6 PKH26-labeled MSC into the contusion epicenter. The transplanted MSC migrated within the injured spinal cord without differentiating into glial or neuronal elements. MSC transplantation was associated with marked changes in the SCI environment, with significant increases in IL-4 and IL-13 levels, and reductions in TNF-a and IL-6 levels. This was associated simultaneously with increased numbers of alternatively activated macrophages (M2 phenotype: arginase-1-or CD206-positive), and decreased numbers of classically activated macrophages (M1 phenotype: iNOS-or CD16/32-positive). These changes were associated with functional locomotion recovery in the MSC-transplanted group, which correlated with preserved axons, less scar tissue formation, and increased myelin sparing. Our results suggested that acute transplantation of MSC after SCI modified the inflammatory environment by shifting the macrophage phenotype from M1 to M2, and that this may reduce the effects of the inhibitory scar tissue in the subacute/chronic phase after injury to provide a permissive environment for axonal extension and functional recovery.
Accumulation of cadmium (Cd) in rice (Oryza sativa L.) grains poses a potential health problem, especially in Asia. Most Cd in rice grains accumulates through phloem transport, but the molecular mechanism of this transport has not been revealed. In this study, we identified a rice Cd transporter, OsLCT1, involved in Cd transport to the grains. OsLCT1-GFP was localized at the plasma membrane in plant cells, and OsLCT1 showed Cd efflux activity in yeast. In rice plants, strong OsLCT1 expression was observed in leaf blades and nodes during the reproductive stage. In the uppermost node, OsLCT1 transcripts were detected around large vascular bundles and in diffuse vascular bundles. RNAi-mediated knockdown of OsLCT1 did not affect xylem-mediated Cd transport but reduced phloem-mediated Cd transport. The knockdown plants of OsLCT1 accumulated approximately half as much Cd in the grains as did the control plants. The content of other metals in rice grains and plant growth were not negatively affected by OsLCT1 suppression. These results suggest that OsLCT1 functions at the nodes in Cd transport into grains and that in a standard japonica cultivar, the regulation of OsLCT1 enables the generation of "low-Cd rice" without negative effects on agronomical traits. These findings identify a transporter gene for phloem Cd transport in plants.heavy metals | food safety
Usual human livers contain two major aldehyde dehydrogenase [(ALDH) aldehyde:NAD+ oxidoreductase] isozymes-i.e., a cytosolic ALDH1 component and a mitochondrial ALDH2 component-whereas o50% of Orientals are "atypical" and have only the ALDH1 isozyme and are missing the ALDH2 isozyme. We previously demonstrated that atypical livers contain an enzymatically inactive but immunologically crossreactive material (CRM) corresponding to the ALDH2 component. The enzymatically active ALDH2 obtained from a usual liver and the CRM obtained from an atypical liver were reduced, S-carboxymethylated, and digested by trypsin. Separation of their digests by high-performance reverse-phase chromatography and by two-dimensional paper chromatography and electrophoresis revealed that ALDH2 contained a peptide sequence of -Glu-Leu-Gly-Glu-Ala-GlyLeu-Gln-Ala-Asn-Val-Gln-Val-Lys-and that the glutamine adjacent to lysine was substituted by lysine in CRM. AU other tryptic peptides, including eight peptides containing S-carboxymethylcysteine, were common in ALDH2 and CRM. It is concluded that a point mutation in the human ALDH2 locus produced the glutamine -I lysine substitution and enzyme inactivation. (1, 2). The specific activity of the atypical /82P2 isozyme is nearly 100 times higher than that of the usual P1P, isozyme (2). It has been shown that the active site cysteine of the usual P, subunit is replaced by histidine in the superactive atypical P2 subunit (2).Virtually all Caucasians have two major ALDH isozymes-i.e., ALDH1 and ALDH2 in their livers-whereas =50% of Orientals are "atypical" in that they have only ALDH1 and are missing ALDH2 (3, 4). A very high incidence (50-80%) of acute alcohol intoxication in Orientals could be related to the absence of active ALDH2 and the presence of superactive PA22 alcohol dehydrogenase isozyme (1, 3). However, the atypical Orientals have an enzymatically inactive but immunologically crossreactive material (CRM) in their livers (5). The amino acid composition, subunit molecular size, and immunological characteristics of CRM were indistinguishable from the corresponding properties of ALDH2 but differed from those of ALDH1 (6). Therefore, CRM should be an abnormal defective protein resulting from a mutation of the ALDH2 locus. Genetic study indicates that two common alleles-i.e., ALDH12 for the usual ALDH2 isozyme and atypical ALDH22 for the defective CRM at the same locus-are codominantly expressed in Orientals (7). The present paper reports the molecular difference between the usual ALDH2 and the enzymatically inactive CRM. MATERIALS AND METHODSALDH and CRM. Two ALDH isozymes-i.e., ALDH1 and ALDH,-were purified from autopsy specimens of human liver as described (6). CRM and ALDH1 were purified from atypical Japanese livers, which contained the ALDH1 isozyme but not the active ALDH2 isozyme, as described (6). Purities of the samples were checked by polyacrylamide gel electrophoresis in the presence of NaDodSO4 as described (6). The proteins were thoroughly dialyzed against water and lyoph...
Long-term survival is possible for selected patients with ATC. To determine the treatment strategy, UICC stage (disease extent) and other prognostic factors (e.g., biologic malignancy grade) should be considered.
The mortalin genes, mot-1 and mot-2, are hsp70 family members that were originally cloned from normal and immortal murine cells, respectively. Their proteins differ by only two amino acid residues but exhibit different subcellular localizations, arise from two distinct genes, and have contrasting biological activities. We report here that the two proteins also differ in their interactions with the tumor suppressor protein p53. The pancytosolic mot-1 protein in normal cells did not show colocalization with p53; in contrast, nonpancytosolic mot-2 and p53 overlapped significantly in immortal cells. Transfection of mot-2 but not mot-1 resulted in the repression of p53-mediated transactivation in p53-responsive reporter assays. Inactivation of p53 by mot-2 was supported by the down-regulation of p53-responsive genes p21 WAF-1 and mdm-2 in mot-2-transfected cells only. Furthermore, NIH 3T3 cells transfected with expression plasmid encoding green fluorescent proteintagged mot-2 but not mot-1 showed an abrogation of nuclear translocation of wild-type p53. These results demonstrate a novel mechanism of p53 inactivation by mot-2 protein.Evidence has been accumulating that inactivation of p53, a tumor suppressor and cellular transcription factor (1), is involved in cellular transformation and immortalization (2-5). Extensive analyses of p53 have defined at least four functional domains, including an amino terminus transactivation domain (amino acids 1-44), a sequence-specific DNA-binding domain (amino acids 100 -300), a carboxyl terminus oligomerization domain, and a regulatory domain (amino acids Ref. 6), and shown that the conformation of p53 and its interactions with other proteins have key roles in its various cellular activities (7,8). Several cellular proteins, including some of the hsp70 family members, have been shown to interact with p53 (9 -12). Although mutational or mdm-2-mediated inactivation of p53 is a common event involved in cellular transformation (1), p53 is inactivated in a considerable number of tumors and transformed cells by an unknown mechanism(s).We initially cloned mortalins mot-1 and mot-2, which code for pancytosolically and perinuclearly distributed members of the hsp70 family of proteins, from normal and immortal murine cells, respectively (13,14). The open reading frames of the two types of murine mortalins differ in two nucleotides, encode proteins differing in two amino acids, arise from distinct genes, and have contrasting biological activities (13-16). RNA in situ hybridization and immunohistochemical studies on mortalin in normal murine tissues showed a higher level of expression in nondividing cell populations than in dividing cells. However, tumor tissues were seen to have a high intensity of mortalin staining by an antibody that reacts with both the mot-1 and mot-2 proteins (17, 18). Mortalin was also identified as PBP-74, mtHSP70, and Grp75 and has been assigned roles in antigen processing, in vivo nephrotoxicity, and radioresistance in independent studies from other groups (19,20)...
Inflorescence structures result from the activities of meristems, which coordinate both the renewal of stem cells in the center and organ formation at the periphery. The fate of a meristem is specified at its initiation and changes as the plant develops. During rice inflorescence development, newly formed meristems acquire a branch meristem (BM) identity, and can generate further meristems or terminate as spikelets. Thus, the form of rice inflorescence is determined by a reiterative pattern of decisions made at the meristems. In the dominant gain-of-function mutant tawawa1-D, the activity of the inflorescence meristem (IM) is extended and spikelet specification is delayed, resulting in prolonged branch formation and increased numbers of spikelets. In contrast, reductions in TAWAWA1 (TAW1) activity cause precocious IM abortion and spikelet formation, resulting in the generation of small inflorescences. TAW1 encodes a nuclear protein of unknown function and shows high levels of expression in the shoot apical meristem, the IM, and the BMs. TAW1 expression disappears from incipient spikelet meristems (SMs). We also demonstrate that members of the SHORT VEGETATIVE PHASE subfamily of MADS-box genes function downstream of TAW1. We thus propose that TAW1 is a unique regulator of meristem activity in rice and regulates inflorescence development through the promotion of IM activity and suppression of the phase change to SM identity.ALOG family | meristem identity | grain yield T he timing of each meristem phase change is crucial in the control of inflorescence architecture (1-3). In grass species, the basic architecture of inflorescence is defined by the spatial arrangement of spikelets, which are small branches containing a variable number of flowers. Among the meristems that are generated from the primary inflorescence meristem (IM) during inflorescence (panicle) development, early ones acquire an indeterminate branch meristem (BM) identity, whereas later ones are specified as determinate spikelet meristems (SMs) (Fig. 1A) (4, 5). The BMs themselves are eventually transformed into SMs after generating a certain number of branches and spikelets (Fig. 1B). Thus, the pattern of SM specification is a primary determinant of grass inflorescence form. Delays in SM specification lead to iterations of branching, resulting in larger panicles that could potentially produce more grain. Conversely, the acceleration of SM specification results in smaller panicles with fewer spikelets. Rice inflorescence development exhibits an additional unique feature in that the IM loses its activity after producing several BMs, leaving a vestige at the tip of the rachis, the inflorescence main stem (Fig. 1A). Therefore, the timing of IM abortion is also a critical factor determining the form of rice inflorescence.The competence of a meristem to become an SM gradually increases during inflorescence development; however, the molecular basis for the timing of SM specification is largely unknown.To date, several genes that control inflorescence form ...
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