Plastidial Promoters NEP promoters

Unambiguous identification of transcription initiation sites for a nuclear-encoded transcription activity (i.e. NEP) became feasible in plants with reduced or elimi- nated transcriptional activity by PEP. Such systems comprise the ribosome-deficient plastids of the monocot albostrians barley and iojap maize mutants (H bschmann and B rner 1998 Silhavy and Maliga 1998a), tobacco Arpo plants (Allison et al. 1996 Hajdukiewicz et al. 1997 Serino and Maliga 1998), Arabi-dopsis lacking PEP due to the...

Leucoplasts and root plastids

Leucoplast is the name given to a general group of plastids, which lack any pigment and are often referred to as non-green plastids. Leucoplasts are very widely distributed in different plant tissues and have a wide range of morphologies and content, the latter being primarily a variation in the type of storage molecules that they accumulate. In fact amyloplasts could be considered a form of leucoplast that has specialised in storing starch. Whilst they are widespread in plant tissues, the...

Linear plastid DNA molecules with discrete ends in WT plastids

Restriction enzymes that cleave plastid DNA rarely once or twice have been used to map the ends of linear molecules in high MW DNA prepared in agarose plugs. When Z. mays plastid DNA was cleaved with an enzyme that cuts once, the predicted linear 140 kbp genome band was observed. In addition, discrete smaller Fig. 4. Models for generation of linear hairpin plastid DNA molecules by a Template strand switching at the replication fork Ellis and Day 1986 , b Intra-strand annealing at inverted...

Plastid division

The fact that plastids can divide as distinct organelles within the cytoplasm of the eukaryotic plant cell was confirmed by several studies in the late 1960s in which populations of plastids were counted and changes in their population size were established in correlation with cell expansion in developing leaves see Pyke 1997 . These studies clearly showed that there were two different points in plastid development where division takes place. Firstly in dividing cells in the meristem,...

Conclusions and outlook

Plastid transformation experiments have demonstrated an efficient homologous recombination pathway in plastids mediated by a RecA-homologue that appears to be active throughout shoot development. The presence of this pathway is consistent with a new emerging view of plastid DNA maintenance in which recombination plays a predominant role. WT plastid DNA is comprised of a mixture of circular and linear DNA molecules, which form a multimeric series from monomer to at least the octomer, and high MW...

Replication origins mapped to the large inverted repeat

Loop Model Dna Replication

Electron-microscopy combined with restriction enzyme digestion enables D-loops and replication bubbles to be mapped onto restriction fragments of plastid DNA. The P. sativum D-loops OriA and OriB flank the 23S ribosomal RNA gene Fig. 6a Meeker et al. 1988 . Unlike most angiosperm plastid genomes P. sativum lacks a large inverted repeat Chapter 3 . Restriction fragments of proplastid DNA with a high frequency of D-loops from N. tabacum BY2 suspension culture cells Fig. 5. Plastid DNA replication...

Info

PEP denotes PEP promoters, NEP represents NEP Type-1 promoters, NEP 0 indicates NEP Type-il promoters, and NEP Pc denotes Pe promoters nd. indicates not yet identified promoters. PEP denotes PEP promoters, NEP represents NEP Type-1 promoters, NEP 0 indicates NEP Type-il promoters, and NEP Pc denotes Pe promoters nd. indicates not yet identified promoters. gene is transcribed from at least three NEP PatpB-255, -502 -488, -611 and two PEP promoters Fig. 5 PatpB-289, -329 Hajdukiewicz et al. 1997...

References

Akita T, Sagisaka S 1995 Functional and structural differences among proplastids as seen by immunogold staining and electron microscopy. Biosci Biotech Biochem 59 14771484 Aldridge C, Maple J, Moller SG 2005 The molecular biology of plastid division in higher plants. J Exp Bot 56 1061-1077 Alexander L, Grierson D 2002 Ethylene biosynthesis and action in tomato a model for climacteric fruit ripening. J Exp Bot 53 2039-2055 Andersson MX, Sandelius AS 2004 A chloroplast-localized vesicular...

DNA recombination in plastids

Linear Dna Recombination

Plastid fusion and DNA recombination between different plastid types are rare in flowering plants. Rapid segregation is observed when two plastid types with different genomes are forced into the same cell by protoplast fusion Morgan and Maliga 1987 . In C. reinhardtii, recombination between parental plastid genomes in exceptional zygotes is well established Gillham 1974 . The development of plastid transformation has demonstrated an active homologous DNA recombination pathway in C. reinhardtii...

Amyloplast structure and morphology

All chloroplasts seem to have the ability to accumulate starch grains within the stroma as a transient store of photosynthetic assimilate. Normally these starch grains are degraded through the dark part of the photoperiod and the products exported. Amyloplasts, however, are a plastid type in which starch accumulation is long term and are mostly found in storage tissues such as tubers and seed endosperm where they are highly abundant. All plant starch is synthesised in the plastid and produced...

Maternal inheritance Chlamydomonas type

In no other plant, chloroplast inheritance has been as thoroughly studied as in the unicellular green alga Chlamydomonas reinhardtii. Chlamydomonas has a single large cup-shaped chloroplast per cell. There exist 'male' and 'female' algae which are morphologically indistinguishable and commonly referred to as mating type mt , 'female' and mating type - mt-, 'male' . Organelle inheritance in Chlamydomonas exhibits several interesting features Umen and Goodenough 2001 . First, chloroplast and...

Paternal leakage

As evident from the above-mentioned exceptional transmission of paternal plastid genes in Chlamydomonas and the discussion of paternal vs. biparental inheritance in gymnosperms, there is a grey zone between uniparental inheritance and biparental inheritance. In most instances, the conclusion that a given species transmits its plastids uniparentally is based on the phenotypic analysis of at most a few thousand progeny plants from reciprocal crosses see 4.2 . Failure to detect variegated...

Plastid DNA polyploidy packaging and segregation Plastid DNA copy number

One thousand to 1,700 copies of plastid DNA are present per cell in Arabidopsis thaliana leaves Zoschke et al. 2007 whilst five thousand to over ten thousand copies of plastid DNA per cell are present in leaves of Pisum sativum Lamppa and Bendich 1979 , Triticum aestivum Day and Ellis 1984 , Spinacia oleracea Lawrence and Possingham 1986 , and Hordeum vulgare Baumgartner et al. 1989 . Fewer plastid genomes per cell are found in other organs containing non-green plastids, such as the roots of P....

Conclusion

Our understanding of some of the cell biology aspects of plastids have improved significantly in the last two decades and the plastid has risen above the status of an organelle that carries out only photosynthesis. The advent of omic technology has the potential for describing subtle differences between different types of plastids and may give clues as to how master controlling genes work, if they exist. Even so, we are still a long way from a clear understanding of what determines a particular...

Chloroplast structure and morphology

Chloroplasts are the most prominent form of plastid occurring in all green plant tissues and enable photosynthetic carbon fixation to occur in addition to a variety of other biochemical processes central to cellular metabolism. Like all plastids, they are bounded by a double plastid envelope membrane, which acts as a major control point for chloroplast import and export as well as being a major site for biochemical synthesis Joyard et al. 1998 . Chloroplasts in leaf mesophyll cells are...

Proplastids

All plastids within a plant are ultimately derived from those progenitor plastids, which are found in meristem cells called proplastids. These in turn have been derived from the few proplastids, which were present in the zygote and derived potentially from both the maternal egg cell and the paternal pollen grain. However, most Angiosperms have mechanisms to exclude or degrade proplastids in the pollen line and hence the plastids present in the majority of plants are inherited maternally...

Biparental inheritance

A small number of angiosperms transmit their plastids biparentally. Working with Pelargonium, Mirabilis, Melandrium, Antirrhinum and Aquilegia, already Erwin Baur and Carl Correns noted in their first experiments on the inheritance of leaf variegations almost hundred years ago Baur 1909, 1910 Correns 1909 that the mode of plastid inheritance may differ between species. While Melandrium, Antirrhinum and Aquilegia mutants transmitted their altered leaf color which, as we now know, represented...

Plastid interconversions

Plastids Interconversion

Although chloroplast differentiation from proplastids, as directed by light, appears the central tenet of plastid biogenesis, there are many examples in which plastids can redifferentiate from pre-existing plastid types and form a different type of plastid Fig. 2 . Such interconversions are controlled by cellular developmental processes as well as environmental or hormonal signals and demonstrate an extreme plasticity in the plastid's functionality within the cell. Although several of these...