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cl
spl
cl
Figure.
Scanning electron microscopy image showing a cutin layer (cl) of smooth
texture over organogenic nodules regenerating shoot primordia (sp).
This cutin layer was specific to nodular organogenic regions and disappeared with
plantlet regeneration. This layer was suggested to control permeability to water and solute
transfer throughout plantlet regeneration.
Lipoxygenases have been related to several processes of growth and development as
well as stress response. Studies of lipoxygenases during organogenic nodule formation in
hop showed that they are developmentally regulated throughout the process [3].
Lipoxygenase activity and lipid peroxides presented a huge increase during the first week
of culture, which could indicate a role for lipoxygenase and lipoxygenase products in
response to wounding in hop, as reported for other systems. Western blotting analysis
showed a de novo synthesis of lipoxygenase (LOX) isoenzymes in response to wounding.
The antibody used detected two different isoenzymes with molecular masses of
approximately 74, and 98 kDa (Fig. 2). A partial cDNA fragment (1000 bp) coding for a
lipoxygenase was cloned through a Reverse Transcriptase- Polimerase Chain Reaction
based approach and may correspond to the most expressed isoenzyme during this period.
As shown using Blast-n (NCBI Database BLAST program) [4] this fragment shares 79 %
identity with Prunus dulcis LOX mRNA.
0d 7d 15d 28d 45d
Figure 2.
Proteins from different culture periods (d-days) after SDS-PAGE and
immunoblotted with polyclonal antisera for LOX. The upper band corresponds
approximately to a 98 kDa isoenzyme whereas the lower one which is less intense
corresponds to a 74 kDa isoenzyme.
Confocal analysis of lipoxygenase immunofluorescence revealed the presence of the
enzyme in cortical cells of induced internodes and in prenodular cells, mostly appearing as
cytoplasmic spots. Some of them were identified as lipid bodies by cytochemical and
double immunofluorescence assays, suggesting the involvement of a lipid-body
lipoxygenase during nodule formation. Immunogold labeling detected lipoxygenase in
peroxisomes, lipid bodies and plastids of nodular cells. The quantification of the labeling
density provided statistical significance to the localization of lipoxygenase (three different
isoenzymes) in the three compartments, which suggested a possible involvement of
