Phloem Transport 21 Sulfur Compounds

In phloem saps and phloem exudates from herbaceous plants, several organic sulfur compounds, namely Cys, Met, g-EC, glutathione (GSH), g-glutamylcysteinylserine, and S-methylmethionine (Ohshima et al. 1990 Kuzuhara et al. 2000 Karley et al. 2002 Bourgis et al. 1999 Mendoza-Cozatl et al. 2008), as well as SO42 , have been detected (Ohshima et al. 1990 Kuzuhara et al. 2000). Further sulfur compounds such as glucosinolates (Brudenell et al. 1999 Chen et al. 2001) and phytochelatins (Chen et al....

Peroxiredoxins

Peroxiredoxins (Prx) are present in many organisms from bacteria to mammals and have function in oxidant defense and signal transduction. Among the ten peroxi-redoxins found in Arabidopsis, the 2-Cys Prx, which is attached at the stromal side of the thylakoid membrane, is the best studied and suggested to be involved in antioxidant defense and protection of photosynthesis (Pulido et al. 2010). The thylakoid lumen contains PrxQ, for which no clear role has been assigned, since the mutant lacking...

Nitrogen Compounds

The main phloem transport forms of nitrogen are amino acids (e.g., Peuke 2010). In general, the phloem-loading mechanism of amino compounds includes amino acid efflux from the symplast of the source tissue to the apoplast and subsequent carrier-mediated transport, which couples proton gradients to the active amino acid transport and accumulation against concentration gradients. Plant amino acid transporters involved in phloem loading are generally characterized by compound overlapping transport...

Photosynthetic Metabolism and Growth Parameters

Under environmental CO2 conditions, the stomatal closure provoked by salinity implies a lower diffusion of CO2 to the inside of the leaf, which results in a decreased assimilation rate. On the contrary, when the environmental CO2 concentrations are increased, although stomata tend to close, there is a higher driving force for the entrance of the CO2 because the gradient of CO2 between the outside and the inside of the leaf increases. In this case, the diffusion is usually higher and, for the...

Biological or Physiological Role of Cd

Cadmium is generally regarded as a non-essential and toxic trace element. However, a Cd-requiring carbonic anhydrase (CA) isolated from the marine diatom T. weissflogii has been characterized as the first Cd-containing enzyme in the biosphere (Lane et al. 2005). Substitution of Zn by Cd to form a Cd-specific CA, particularly under conditions of low Zn, plays a biological role in carbon acquisition and photosynthesis of some marine phytoplanktons (Lane and Morel 2000). It is this important...

Metal Transporters in Hyperaccumulators

Homeostasis Plant

The transport of metals across plasma membranes by means of primary and secondary active transporters is of central importance in the metal homeostasis network in plants (Kotrba et al. 2009). With the use of genetic and molecular Fig. 1 Molecular and physiological mechanisms involved in Cd hyperaccumulation and detoxification (a-d), and their evolutionary significance for Cd hyperaccumulators (e-g). (a) Root foraging for Cd is a strategy that hyperaccumulator species employ to acquire high...

Grazing Deterrent Effect and Toxicity of Various Lichen Compounds

There are few studies quantifying the herbivory-deterrent effect and or toxicity of specific lichen compounds for herbivores. Table 2 summarizes documented antiherbivore and toxic effects of lichen compounds. Removal of secondary compounds from Vulpicida pinastri and from H. physodes greatly increased survival of larvae of the moth E. depressum, whereas acetone rinsing of Parmelia sulcata had no long-term impacts on the larvae (Poykko et al. 2005). These data indicate that vulpinic and...

Oxygen Evolving Complex Associated Proteins

The mechanism of oxygen evolution by PSII has remained conserved during evolution from cyanobacteria to higher plants. The oxygen-evolving complex (OEC) is a Mn4CaCl2 ion cluster (Loll et al. 2005) whose binding environment is optimized by several lumenal extrinsic PSII subunits. The accepted view is that plants and green algae have PsbO, PsbP, and PsbQ as OEC-associated proteins, whereas cyanobacteria have PsbO, PsbP, PsbQ, PsbV, and PsbU, the last two being lost during evolution of higher...

Signaling Events During CAM Modulation by Water Availability

Virtually all C3-CAM facultative plants respond to water stress with a rapid increase in the abundance of transcripts and proteins of CAM-related enzymes, which in most cases is followed by the induction of functional CAM (Brulfert et al. 1993 Cushman and Borland 2002 Freschi et al. 2010a Luttge 2004a Taybi et al. 1995). Depending on the intensity and duration of the water stress, typical CAM or CAM idling can be induced (Brulfert et al. 1996 Freschi et al. 2010b Guralnick and Ting 1986 Luttge...

Signaling Events During CAM Modulation by Salinity

One of the main consequences of salinity is osmotic stress therefore, the higher WUE provided by the CAM syndrome could be interpreted as an obvious adaptive advantage for plants living in high salinity conditions. However, contrary to expectation, constitutive or inducible CAM is not commonly found among true halo-phytes (Luttge 2004b). Currently, the best known example of CAM halophyte is M. crystallinum, which displays intense C3-CAM switch when challenged with high salinity conditions...

Mechanisms of Cd Hyperaccumulation and Detoxification in Heavy Metal Hyperaccumulators How Plants Cope with Cd

Rong-Liang Qiu, Ye-Tao Tang, Xiao-Wen Zeng, Palaniswamy Thangavel, Lu Tang, Yuan-Yuan Gan, Rong-Rong Ying, and Shi-Zhong Wang 2 Cd Accumulation in 2.1 Rhizosphere Mobilization and Root 2.2 Cd Translocation from Roots to Shoots in 2.3 Cd Accumulation in 3 Cd 3.1 Complexation of Cd by 3.2 Antioxidant Defense 3.3 Cell Wall Binding and Vacuole 4 Evolution of Cd 4.1 Elemental 4.2 A Biological or Physiological Role of 5 Future References R.L. Qiu (*) Y.T. Tang S.Z. Wang School of Environmental...

Biosynthesis of Hydrocarbons 31 Alkanes

The pathway for alkane synthesis in cyanobacteria seems to proceed via decarbonylation of fatty aldehydes Schirmer et al. 2010 , the major route for alkane synthesis in most organisms Ladygina et al. 2006 . The decarbonylation pathway implies the involvement of the fatty acyl-CoA or fatty acyl-ACP reductase FadR EC 1.2.1.50 and fatty aldehyde decarbonylase FAD EC 4.1.99.5 Walsh et al. 1998 Ladygina et al. 2006 Fig. 2 . Gene sequences for FadR and FAD have recently been identified from several...

Metabolic Engineering of Cyanobacteria for Direct Conversion of CO2 to Hydrocarbon Biofuels

Cyanobacteria Fig

2 Fatty Acid Metabolism in Cyanobacteria 3 Biosynthesis of Hydrocarbons 4 Conclusions and Perspectives References Abstract Cyanobacteria are oxygenic photosynthesizers like plant and algae and hence can capture CO2 via the Calvin cycle and convert it to a suite of organic compounds. They are Gram-negative bacteria and are well suited for synthetic biology and metabolic engineering approaches for the phototrophic production of various desirable biomolecules, including ethanol, butanol,...