Apoplast acidification in growing barley (Hordeum vulgare L.) leaves
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Tartalom: http://real.mtak.hu/2974/
Archívum: MTA Könyvtár
Gyűjtemény: Status = Unpublished

Type = Thesis
Cím:
Apoplast acidification in growing barley (Hordeum vulgare L.) leaves
Létrehozó:
Visnovitz, Tamás
Dátum:
2011-10
Téma:
QK10 Plant physiology / növényélettan
Tartalmi leírás:
Apoplast acidification associated with growth is well-documented in roots, coleoptiles
and internodes but not in leaves. In the present project on barley (Hordeum vulgare L.)
advantage was taken of the high cuticle permeability in the elongation zone of leaves to
measure apoplast pH and growth in response to application of test reagents. The role of
the plasma membrane H+-ATPase (PM-H+-ATPase) and K+ in this process was of
particular interest. An in vitro gel system with bromocresol purple as pH indicator, pH
microelectrodes and pH-sensitive fluorescence dye combined with confocal microscopy
were used to monitor apoplast pH. Growth was measured in parallel or in separate
experiments using a linear variable differential transformer (LVDT). Test reagents which
blocked (vanadate) or stimulated (fusicoccin) PM-H+-ATPase, or which reduced (NH4
+,
Cs+, tetraethylammonium) K+ uptake were applied. Plasma membranes were isolated
from growing and mature leaf tissue and used to determine the activity (ATPase assay)
and abundance (Western blotting) of PM-H+-ATPase protein. Protein localisation was
studied by immunohistochemistry and expression of mRNA quantified using real time
PCR (qPCR). Apoplast pH was by up to 1.0 pH unit lower in growing compared to nongrowing
leaf tissue. Depending on the K+ concentration in the bathing medium used
during electrophysiological analyses, apoplast pH in the elongation zone ranged from
pH 4.8 (0.1 mM K+) to pH 5.8 (10 mM K+). In the emerged blade, apoplast pH remained
at about pH 5.8 irrespective of the K+ concentration in the bathing medium Growth was
more responsive to test reagents than to changes in apoplast pH. Expression of PM-H+-
ATPase was comparable between growing and non-growing leaf regions when
expression was related to per unit extracted RNA or cell number. However, when
expression was related to per unit surface area of plasma membrane, expression of
PM-H+-ATPase was about twice as high in growing compared to non-growing leaf
tissue. The same applied to the protein level and activity of PM-H+-ATPase.
Immunohistochemical analyses showed that PM-H+-ATPase was present in all living
leaf tissues, particular in those (guard cells, phloem, and xylem parenchyma)
associated with high rates of trans-membrane solute transport. It is concluded that leaf
cell expansion in barley depends on the activity of the PM-H+-ATPase and K+ transport
processes. The higher surface density of PM-H+-ATPase activity in growing barley leaf
tissue aids apoplast acidification and growth. A H+ / K+ co-transport system may play a
key role in linking growth with apoplast pH, H+ pump activity and K+-uptake.
Típus:
Thesis
NonPeerReviewed
Formátum:
text
Azonosító:
Visnovitz, Tamás (2011) Apoplast acidification in growing barley (Hordeum vulgare L.) leaves. PhD thesis, University College Dublin, Dublin, Ireland.
Kapcsolat: