Secondary somatic embryogenesis and applications in plant breeding

Summary Secondary somatic embryogenesis is the phenomenon whereby new somatic embryos are initiated from somatic embryos. Such cultures have been described in at least 80 Gymnosperm and Angiosperm species. In the initial step (primary somatic embryogenesis) such cultures have to be started from plant explants. In general, primary somatic embryogenesis from vegetative plant explants is, indirect and mostly driven by auxin (AUX) or auxin and cytokinin (AUX/CYT) supplemented media, whereas, from zygotic embryos it is direct and driven, to a larger extent, by CYT or growth regulator free media. Primary somatic embryogenesis from floral plant explants is between these two extremes. Indirect and direct somatic embryogenesis should be seen as two extremes of one continuum: in indirect somatic embryogenesis the embryos develop up to the (pre)-globular stage and in direct somatic embryogenesis to mature stages before they are subjected to secondary embryogenesis. In general, secondary embryogenesis requires no growth regulators in species with CYT driven primary embryogenesis. Whereas, continuous exposure to growth regulators is needed in species with CYT/AUX or AUX driven primary embryogenesis.In most species somatic embryos can be converted into shoots, although the frequencies are mostly low. In general, somatic embryos induced by growth regulator free or CYT supplemented media meet more difficulties in shoot development than embryos induced by AUX supplemented media. Applications of secondary somatic embryogenesis for plant breeding are discussed.     

The performance of double or mixed pollinations with compatible and self-incompatible or incongruous pollen of pear and apple

Summary Six pear and five apple trials were carried out to ascertain the outcome of combinations of compatible pollen (C) with self (S) or incongruous pollen (I) as to the pollination index (PI=seeds/pollinated flower). The PI of the mixture C+I (1:5) was consistently depressed as compared to that of the control C. The results of the double pollinations S/C and I/C were affected by the temperature at pollination; their PI's at <15°C were twice as high as those at >15°C, being well above and below the PI of C in the former and latter case respectively. The opposite was true for the C/S combination, the PI of which increased with the pollination temperature; the PI of C/I did not differ much from the PI of C, irrespective of temperature. The conclusion was reached that the interaction previously and presently found between compatible and self-incompatible pollen also exists to a fair extent between compatible and incongruous pollen. However, in pear neither the mentor nor the pioneer pollen technique proved to aid its hybridization with apple, the formation of self seed was not observed either. In apple the production of apple × pear hybrids was likewise doubtful, but the double pollinations S/C and C/S formed 4–10% self seed.     

Avenin diversity analysis of the genus Avena (oat). Relevance for people with celiac disease

Oat is widely consumed by people with celiac disease (CD). Its safety has been disputed because two peptides from oat avenins can be recognized as T cell epitopes by some CD patients. Differential signals of gluten-specific monoclonal antibodies and in-vitro T cells to oat varieties have suggested the existence of differences in immunogenicity. We aimed to clarify the nature of such responses by cloning avenin genes from 13 Avena species. A single oat plant contained up to 10 avenin genes. Avenin proteins clustered in four groups of which two contained the two avenin CD epitopes. All Avena species examined harbored avenins of these two groups, and as a consequence all contained avenins with the two avenin-specific epitopes, which makes it very unlikely to find oat cultivars that are devoid of these sequences. The established gluten epitopes from wheat, rye and barley were not present in oat avenins; some variants with two and three amino acid substitutions occurred, but they were predicted not to resist proteolysis in the gastro-intestinal tract. Perfect recognition sites of antibodies R5 and G12 were also not present in avenins. Thus, their signals to oat should not be interpreted as differences in immunogenicity for CD patients.     

A survey of the skidder fleet of Central,Eastern and Southern Europe

European Journal of Forest Research - As a generalization, harvested timber is extracted from forests either as trees or stems by skidders or as logs by forwarders. Coupled with harvesters,...     

Towards genetic transformation in the monocot Alstroemeria L.

The successful application of plant biotechnology to Alstroemeria improvement will largely depend on the availability of an efficient regeneration/transformation system. Regeneration in Alstroemeria is accomplished from nodular embryogenic callus initiated from zygotic embryos. Histological studies of embryogenic callus initiation from 4-weeks old cultured ovules revealed that the outermost layers of the protoderm of the embryogenic nodules divided to form either a new nodule or aproembryo. Transient gene expression after particle bombardment of nodular embryogenic callus was optimized using DNA of pAHC25. The highest β-glucuronidase expression was found when the GUS gene was under control of the maize ubiquitin promoter, the target tissue was placed 5 cm below the microcarrier launch assembly and when the rupture disc-breakage point was between 650–900 psi. Kanamycin blocked regeneration of somatic embryos, however, did not block growth of nodular embryogenic callus. With phosphinothricin both callus growth and regeneration were blocked. Bombardment of nodular embryogenic callus with DNA of pAHC25 combined with selection on medium containing phosphinothricin resulted in putative transgenic chimeric. Friable calli were selected from nodular embryogenic callus and used to initiate suspensions. These cell suspensions were subjected to transformation by particle bombardment using DNA of pAHC25 and resulted in a stable transformed friable callus line after selection based on luciferase activity. Even after 2 years of maintenance this callus line was luciferase positive and the Polymerase Chain Reaction analysis demonstrated the presence of the introduced gene in this friable callus line. This revised version was published online in July 2006 with corrections to the Cover Date.     

Lipids, buoyancy and the seasonal vertical migration of Calanus finmarchicus

The copepod Calanus finmarchicus remains in diapause for up to 5 months in the cold (<0.5°C) deep (>700 m) waters of the Faroe–Shetland Channel of the north-western approaches to the North Sea. While in diapause, C. finmarchicus has a high lipid content, up to 76% of dry weight, mostly in the form of wax esters. The question we address here is how copepods with such a high content of buoyant lipids can remain in diapause at depth for an extended period of time? The corollary to this is how this lipid content hinders and/or assists the copepods in their seasonal vertical migration? Part of the answer is due to the physical properties of wax esters. These have a thermal expansion and compressibility higher than that of sea water. Thus, depending on their relative composition (i.e. wax esters/water/protein/chitin), a copepod that is positively buoyant in warm surface waters can become neutrally buoyant in cold deep water. We develop a simple three component physical model of a copepod to explore how and where they attain neutral buoyancy, how the lipid content can aid in their ascent, and what fraction of the lipids can be utilized in ascent in gonad/egg formation while maintaining observed ascent rates. As well as being an energy reserve, the results show that rather than being a barrier to vertical migration, wax esters serve as an important regulator of buoyancy.