Bariloche protein symposium argentine society for biochemistry and molecular biology

147
BIOCELL, 27 (Suppl. I), 2003
PL-P54.
ANTIOXIDANT RESPONSES IN APPLES EXPOSED TO
SUNBURN INJURY
Colavita Graciela M.
1
, Orioli Gustavo A.
2
 and Venturino Andrés
1
1
Facultad Ciencias Agrarias, UNComahue, Río Negro; 
2
UNdel
Sur, Bahía Blanca, Argentina. E-mail: [e-mail]
We reported previously that fruit development under solar stress
was accompanied by an increase in lipid peroxides positively
correlated to sunburn damage. In the present study we examined
changes in ascorbate (AsA), glutathion (GSH), superoxide
dismutase (SOD) and catalase (CAT) in the adaptive development
of sun-exposed vs. shaded fruit of apple cultivars “Braeburn” (BR)
and “Red Delicious” (RD). Reaching maturity, SOD increased
sharply in shaded fruits (1527 U/gFW in BR and 436 U/gFW in
RD), and was additionally induced by sun exposure, mainly in
BR where it peaked to 8X and then decreased. CAT showed
different profiles between both cultivars, increasing in RD and
decreasing in BR, and was induced by solar radiation, being lower
in BR (15 IU/gFW ) vs. RD (36 IU/gFW). AsA content increased
early in sun-exposed fruits, being always higher in BR, and
declining to harvest (112 to 88 nmole/gFW). GSH content was
similar in shaded fruits and the increase by solar exposure was
higher in RD (160 nmole/gFW, 2X vs BR). Sun exposure of fruits
from early stages would cause an adaptive response related to
induction of antioxidant compounds and enzymes in both cultivars.
The higher sensitivity of BR fruits may be related to reduction in
CAT with high SOD levels, and to a higher solar exposure due to
morphological and physiological characteristics.
PL-P55.
REACTIVE OXYGEN SPECIES (ROS) AND SALICYLIC
ACID (SA) SIGNAL PROLINE ACCUMULATION IN
PLANT:PATHOGEN INCOMPATIBLE INTERACTIONS
Fabro, Georgina
1
; Pavet, Valeria
1
; Kovacz, Izabella
2
; Szabados,
Lászlò
2
 and Alvarez, M.E.
1
1
CIQUIBIC. Dpto. Química Biológica, Fac. Cs. Químicas, UNC,
Córdoba, Argentina. 
2
Biological Research Center, Szeged,
Hungary. E-mail: [e-mail]
L-proline (Pro) accumulation is a classical response against abiotic
stresses (drought, salinity and cold). Although its protective role
is not well understood, it is thought to function as compatible
osmolyte and ROS scavenger. We recently demonstrated that Pro
accumulation is also triggered by biotic injuries. Pro content
increases in A. thaliana tissues developing incompatible
plant:pathogen interactions with avirulent races of Pseudomonas
syringae pv.tomato  (Pst) activating a Hypersensitive Response
(HR). Pro increase in hr correlates with transcriptional activation
of Pro biosynthetic (AtP5CS2) and catabolic (ProDH) genes.
AtP5CS2:GUS and  AtP5CS2:LUC  transgenes are induced inside
and around HR lesions where Pro also accumulates. To investigate
whether  Pst-induced Pro enhancement requires signaling
components of the HR, we evaluated the role of ROS and SA in
the activation of this novel response. We quantified Pro levels
and  AtP5CS2 expression in: i) SA- and ROS-treated wild type
plants, ii) SA-deficient mutants. We analyzed both responses in
interactions involving two avirulence genes (Pst avrRpm1 and Pst
avrRps2) which have different SA requirements. As other defenses,
pro accumulation was more sensitive to SA deficiency when
elicited by Pst avrRps2. Meanwhile, exogenous ROS activate both
Pro enhancement and AtP5CS2 expression. SA may then potentiate
Pro accumulation affecting early steps of the defense cascade,
probably involving ROS as intermediate signal.
PL-P56.
CLONING AND  CHARACTERIZATION  OF
FRUCTOSYLTRANSFERASES GENES IN GRAMINEAE
del Viso Florencia, Heinz Ruth and Puebla Andrea F.
Instituto de Biotecnología, CICVyA, INTA- Castelar, Argentina.
E-mail: [e-mail]
Abiotic stresses induce complex responses in plants, affecting
productivity of agronomically important crops. Acclimation to low
temperatures involves biochemical and physiological processes
that are associated to cold tolerance. Accumulation of compatible
solutes was found during cold acclimation and many Graminean
species accumulate fructans (fructose polymers) after being
exposed to chilling temperatures. Fructans are produced in the
vacuole by the action of fructosyltransferases and might be related
to low temperatures tolerance in Gramineae species. The aim of
this work was to isolate and characterize genes codifying for
fructosyltransferases from Gramineae species: a native one,
Bromus pictus and an agronomically interesting species, like
wheat. The isolation of these genes will allow expression studies
involving transformation of species that lack fructan metabolism
and are susceptible to low temperatures and drought. PCR
techniques (RT-PCR, 5´ and 3´ RACE) and a genomic library were
used to isolate homologue sequences with fructan genes in B.
pictus. A cDNA and a genomic clone from B.pictus were isolated
showing high similarity with Graminean fructosyltransferases
genes. A genomic BAC library of T. monococcum was screened
with a fructosyltransferase cDNA. Sixteen positive clones were
found and a 4 kb fragment was subcloned and analyzed. Sequence
analysis showed high similarity with fructosyl transferases and
invertases from Gramineae species, but reveled low similarity with
cDNAs that codify fructan enzymes recently isolated from Triticum
aestivum.
LI-P1.
INSULIN INCREASED 
∆6 DESATURASE ACTIVITY IN
LIVER RAT BY PRE- AND POST-TRANSLATIONAL
MECHANISMS
Rimoldi Omar J., Finarelli Gabriela S. and Brenner Rodolfo R.
Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP).
Facultad de Ciencias Médicas, UNLP, 60 y 120 La Plata. E-mail:
[e-mail]
It has been recognized that rat liver microsomal 
∆6 desaturase
activity is defective in experimental diabetes, fact that may be
reverted by means of insulin treatment. In the present study, we
used streptozotocin-induced diabetic rats in order to determine
the regulatory role of insulin on the activity and gene expression
of hepatic 
∆6 desaturase. Insulin supplementation in diabetic rats
rapidly (2 h) restored the specific activity of the enzyme, whereas
the level of mRNA and desaturase protein remained at the same
level to that of control diabetic animals. On the other hand,
desaturase insulin-induced up-regulation of gene transcriptions
resulted in a 17-fold increase in desaturase transcript amounts
after 18 h, with a concomitant increase of the specific activity of
the enzyme. These results suggest that the insulin-induced 
∆6
desaturase activity arises from two responses. First, a preexisting
latent desaturase becomes activated around 2 h after insulin
administration. This might include the release sequestered enzyme
or activation by post-translational modification. Second, the
amounts of the desaturase transcript are increased as a result of
insulin-induced  gene transcription by pre-translational events.

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