Molecular characterization and genetic mapping of DNA sequences encoding the Type I chlorophyll a/b-binding polypeptide of photosystem I in Lycopersicon esculentum (tomato)

We report the isolation and characterization of a tomato nuclear gene encoding a chlorophyll a/b-binding (CAB) protein of photosystem I (PSI). The coding nucleotide sequence of the gene, designated Cab -6B, is different at eight positions from that of a previously isolated cDNA clone derived from the Cab -6A gene, but the two genes encode identical proteins. Sequence comparison with the cDNA clone revealed the presence of three short introns in Cab -6B. Genetic mapping experiments demonstrate that Cab -6A and Cab -6B are tightly linked and reside on chromosome 5, but the physical distance between the two genes is at least 7 kilobases. Cab -6A and Cab -6B have been designated Type I PSI CAB genes. They are the only two genes of this branch of the CAB gene family in the tomato genome, and they show substantial divergence to the genes encoding CAB polypeptides of photosystem II. The Type I PSI CAB genes, like the genes encoding PSII CAB proteins, are highly expressed in illuminated leaf tissue and to a lesser extent in other green organs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43459/1/11103_2004_Article_BF00166457.pd

HFR1 Is Crucial for Transcriptome Regulation in the Cryptochrome 1-Mediated Early Response to Blue Light in Arabidopsis thaliana

Cryptochromes are blue light photoreceptors involved in development and circadian clock regulation. They are found in both eukaryotes and prokaryotes as light sensors. Long Hypocotyl in Far-Red 1 (HFR1) has been identified as a positive regulator and a possible transcription factor in both blue and far-red light signaling in plants. However, the gene targets that are regulated by HFR1 in cryptochrome 1 (cry1)-mediated blue light signaling have not been globally addressed. We examined the transcriptome profiles in a cry1- and HFR1-dependent manner in response to 1 hour of blue light. Strikingly, more than 70% of the genes induced by blue light in an HFR1-dependent manner were dependent on cry1, and vice versa. High overrepresentation of W-boxes and OCS elements were found in these genes, indicating that this strong cry1 and HFR1 co-regulation on gene expression is possibly through these two cis-elements. We also found that cry1 was required for maintaining the HFR1 protein level in blue light, and that the HFR1 protein level is strongly correlated with the global gene expression pattern. In summary, HFR1, which is fine-tuned by cry1, is crucial for regulating global gene expression in cry1-mediated early blue light signaling, especially for the function of genes containing W-boxes and OCS elements

Inapplicability of advance directives in a paternalistic setting: the case of a post-communist health system

<p>Abstract</p> <p>Background</p> <p>The Albanian medical system and Albanian health legislation have adopted a paternalistic position with regard to individual decision making. This reflects the practices of a not-so-remote past when state-run facilities and a totalitarian philosophy of medical care were politically imposed. Because of this history, advance directives concerning treatment refusal and do-not-resuscitate decisions are still extremely uncommon in Albania. Medical teams cannot abstain from intervening even when the patient explicitly and repeatedly solicits therapeutic abstinence. The Albanian law on health care has no provisions regarding limits or withdrawal of treatment. This restricts the individual's healthcare choices.</p> <p>Discussion</p> <p>The question of <it>'medically futile' </it>interventions and pointless life-prolonging treatment has been discussed by several authors. Dutch physicians call such interventions '<it>medisch zinloos</it>' (<it>senseless</it>), and the Netherlands, as one of the first states to legislate on end-of-life situations, actually regulates such issues through appropriate laws. In contrast, leaving an 'advance directive' is not a viable option for Albanian ailing individuals of advanced age. Verbal requests are provided during periods of mental competence, but unfortunately such instructions are rarely taken seriously, and none of them has ever been upheld in a legal or other official forum.</p> <p>Summary</p> <p>End-of-life decisions, treatment refusal and do-not-resuscitate policies are hazardous options in Albania, from the legal point of view. Complying with them involves significant risk on the part of the physician. Culturally, the application of such instructions is influenced from a mixture of religious beliefs, death coping-behaviors and an immense confusion concerning the role of proxies as decision-makers. Nevertheless, Albanian tradition is familiar with the notion of '<it>amanet</it>', a sort of living will that mainly deals the property and inheritance issues. Such living wills, verbally transmitted, may in certain cases include advance directives regarding end-of-life decisions of the patient including refusal or termination of futile medical treatments. Since these living wills are never formally and legally validated, their application is impossible and treatment refusal remains still non practicable. Tricks to avoid institutional treatment under desperate conditions are used, aiming to provide legal coverage for medical teams and relatives that in extreme situations comply with the advice of withholding senseless treatment.</p

The tomato Cab -4 and Cab -5 genes encode a second type of CAB polypeptides localized in Photosystem II

The photosynthetic apparatus of plant chloroplasts contains two photosystems, termed Photosystem I (PSI) and Photosystem II (PSII). Both PSI and PSII contain several types of chlorophyll a/b-binding (CAB) polypeptides, at least some of which are structurally related. It has been previously shown that multiple genes encoding one type of PSII CAB polypeptides exist in the genome of many higher plants. In tomato, there are at least eight such genes, distributed in three independent loci. Genes encoding a second type of CAB polypeptides have been isolated from several plant species, but the precise location of the gene products has not been determined. Here we show that tomato has two unlinked genes encoding this second type and that this type of CAB polypeptide is also localized in PSII.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43458/1/11103_2004_Article_BF00015643.pd

Chemical Magnetoreception: Bird Cryptochrome 1a Is Excited by Blue Light and Forms Long-Lived Radical-Pairs

Cryptochromes (Cry) have been suggested to form the basis of light-dependent magnetic compass orientation in birds. However, to function as magnetic compass sensors, the cryptochromes of migratory birds must possess a number of key biophysical characteristics. Most importantly, absorption of blue light must produce radical pairs with lifetimes longer than about a microsecond. Cryptochrome 1a (gwCry1a) and the photolyase-homology-region of Cry1 (gwCry1-PHR) from the migratory garden warbler were recombinantly expressed and purified from a baculovirus/Sf9 cell expression system. Transient absorption measurements show that these flavoproteins are indeed excited by light in the blue spectral range leading to the formation of radicals with millisecond lifetimes. These biophysical characteristics suggest that gwCry1a is ideally suited as a primary light-mediated, radical-pair-based magnetic compass receptor

The Protein Phosphatase 7 Regulates Phytochrome Signaling in Arabidopsis

The psi2 mutant of Arabidopsis displays amplification of the responses controlled by the red/far red light photoreceptors phytochrome A (phyA) and phytochrome B (phyB) but no apparent defect in blue light perception. We found that loss-of-function alleles of the protein phosphatase 7 (AtPP7) are responsible for the light hypersensitivity in psi2 demonstrating that AtPP7 controls the levels of phytochrome signaling. Plants expressing reduced levels of AtPP7 mRNA display reduced blue-light induced cryptochrome signaling but no noticeable deficiency in phytochrome signaling. Our genetic analysis suggests that phytochrome signaling is enhanced in the AtPP7 loss of function alleles, including in blue light, which masks the reduced cryptochrome signaling. AtPP7 has been found to interact both in yeast and in planta assays with nucleotide-diphosphate kinase 2 (NDPK2), a positive regulator of phytochrome signals. Analysis of ndpk2-psi2 double mutants suggests that NDPK2 plays a critical role in the AtPP7 regulation of the phytochrome pathway and identifies NDPK2 as an upstream element involved in the modulation of the salicylic acid (SA)-dependent defense pathway by light. Thus, cryptochrome- and phytochrome-specific light signals synchronously control their relative contribution to the regulation of plant development. Interestingly, PP7 and NDPK are also components of animal light signaling systems

Isolation and sequence of a tomato cDNA clone encoding subunit II of the photosystem I reaction center

We report here the isolation and nucleotide sequence of a cDNA clone encoding a phtosystem I polypeptide that is recognized by a polyclonal antibody prepared against subunit II of the photosystem I reaction center. The transit peptide processing site was determined to occur after Met 50 by N terminal sequencing. The decuced sequence of this protein predicts that the polypeptide has a net positive charge (pI=9.6) and no membrane spanning regions are evident from the hydropathy plot. Based on these considerations and the fact that subunit II is solubilized by alkali treatment of thylakoids, we concluded that subunit II is an extrinsic membrane protein. The absence of hydrophobic regions characteristic of thylakoid transfer domains furthermore implies that subunit II is localized on the stromal side of the membrane.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43419/1/11103_2004_Article_BF00014949.pd

Nucleo-cytoplasmic transport of proteins and RNA in plants

Merkle T. Nucleo-cytoplasmic transport of proteins and RNA in plants. Plant Cell Reports. 2011;30(2):153-176.Transport of macromolecules between the nucleus and the cytoplasm is an essential necessity in eukaryotic cells, since the nuclear envelope separates transcription from translation. In the past few years, an increasing number of components of the plant nuclear transport machinery have been characterised. This progress, although far from being completed, confirmed that the general characteristics of nuclear transport are conserved between plants and other organisms. However, plant-specific components were also identified. Interestingly, several mutants in genes encoding components of the plant nuclear transport machinery were investigated, revealing differential sensitivity of plant-specific pathways to impaired nuclear transport. These findings attracted attention towards plant-specific cargoes that are transported over the nuclear envelope, unravelling connections between nuclear transport and components of signalling and developmental pathways. The current state of research in plants is summarised in comparison to yeast and vertebrate systems, and special emphasis is given to plant nuclear transport mutants

Determination of steady-state mRNA levels of individual chlorophyll a/b binding protein genes of the tomato cab gene family

The steady-state levels of mRNA produced by 14 genes encoding members of the tomtato chlorophyll a/b binding protein family were quantified. All genes were found to be expressed in leaf tissue, but the mRNAs accumulated to significantly different levels. The transcripts of cab 1A, cab 1B, cab 3A and cab 3B, encoding the Type I LHC proteins of photosystem II, are abundant, while low levels were measured for mRNAs encoding the Type II LHC II and the LHC I proteins. Sequences from the 5′ upstream regions (−400 to translational start) of some cab genes were determined in this study, and a total of 16 tomato cab gene promoters for which sequences are now available were analyzed. Significant sequence conservation was found for those genes which are tandemly linked on the chromosome. However, the level of sequence conservation is different for the different cab subfamilies, e.g. 85% similarity between cab 1A and cab 1D vs. 45% sequence similarity between cab 3A and cab 3C upstream sequences. Characteristic GATA repeats with a conserved spacing were found in 5′ upstream sequences of cab 1AD, cab 3 A-C, cab 11 and cab 12. The consensus sequence CCTTATCAT, which is believed to mediate light responsiveness, was found at different locations in the upstream sequences of cab 6B, cab 7, cab 8, cab 9, cab 10A, cab 10B and cab 11. In 11 out of 15 genes the transcription initiation site was found to center on the triplet TCA.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47581/1/438_2004_Article_BF00280298.pd

Signal processing and transduction in plant cells: the end of the beginning?

Plants have a very different lifestyle to animals, and one might expect that unique molecules and processes would underpin plant-cell signal transduction. But, with a few notable exceptions, the list is remarkably familiar and could have been constructed from animal studies. Wherein, then, does lifestyle specificity emerge