Differential Expression of the
S-Adenosyl-L-Methionine Synthase Genes
during Pea Development1
Lourdes Gómez-Gómez2 and
Pedro Carrasco*
Departament de Bioquímica i Biologia Molecular, Universitat
de València, Dr. Moliner 50, Burjassot, València,
E-46100 Spain
Two
genes coding for S-adenosyl-L-methionine
synthase (SAMS, EC 2.5.1.6) were previously isolated from pea
(Pisum sativum) ovaries. Both SAMS genes
were highly homologous throughout their coding regions but showed a
certain degree of sequence divergence within the 5
and the 3
untranslated regions. These regions have been used as gene-specific
probes to analyze the differential expression of SAMS1
and SAMS2 genes in pea plants. The ribonuclease protection assay revealed different expression patterns for each individual gene. SAMS1 was strongly expressed in nearly
all tissues, especially in roots. SAMS2 expression was
weaker, reaching its highest level at the apex. Following pollination,
SAMS1 was specifically up-regulated, whereas
SAMS2 was expressed constitutively. The up-regulation of
SAMS1 during ovary development was also observed in
unpollinated ovaries treated with auxins. In unpollinated ovaries an
increase in SAMS1 expression was observed as a
consequence of ethylene production associated with the emasculation
process. In senescing ovaries both SAMS1 and
SAMS2 genes showed increased expression. Ethylene
treatment of unpollinated ovaries led to an increase in the
SAMS1 mRNA level. However, SAMS2
expression remained unchangeable after ethylene treatment, indicating
that SAMS2 induction during ovary senescence was not
ethylene dependent. SAMS mRNAs were localized by in situ
hybridization at the endocarp of developing fruits and in the ovules of
senescing ovaries. Our results indicate that the transcriptional
regulation of SAMS genes is developmentally controlled
in a specific way for each gene.
1
This research was supported by grant no.
PB92-0018-C02-02 from Dirección General de Investigación
Científica y Tecnológica (Spain) to P.C. L.G.G. was
funded by the Conselleria d'Educació i Ciència de la
Generalitat Valenciana.
2
Present address: Friedrich Miescher-Institut,
Postfach 2543, CH-4002 Basel, Switzerland.
*
Corresponding author; e-mail pedro.carrasco{at}uv.es; fax
34-6-3864635.
Plant Physiol. (1998) 117: 397-405
Copyright Clearance Center: 0032-0889/98/117/0397/09
© 1998 American Society of Plant Physiologists