INVESTIGADORES
GOLDRAIJ ariel
artículos
Título:
Arginase is inoperative in developing soybean embryos
Autor/es:
ARIEL GOLDRAIJ; JOE POLACCO
Revista:
PLANT PHYSIOLOGY.
Editorial:
American Society of Plant Biologists
Referencias:
Lugar: Rockville, MD, USA; Año: 1999 vol. 119 p. 297 - 303
ISSN:
0032-0889
Resumen:
Arginase (EC 3.5.3.1) transcript level and activity were measured
in soybean (Glycine max L.) embryos from the reserve deposition
stage to postgermination. Using a cDNA probe for a small soybean
arginase gene family, no transcript was detected in developing
embryos. However, arginase transcripts increased sharply on germination,
reaching a maximum at 3 to 5 d after germination. There
was low but measurable in vitro arginase specific activity in developing
embryos (less than 6% of seedling maximum). During germination
arginase specific activity increased in parallel with the
sharply increasing arginase transcript level. Seedling arginase activity
was largely localized in cotyledons. Arginase activity was assayed
in vivo by measuring urea accumulation in a urease-deficient
mutant. No urea was detected in developing embryos, whereas
accumulated urea paralleled arginase specific activity and transcript
level in germinating seedlings. As in planta embryos, cultured
cotyledons did not accumulate urea when arginine (Arg) was provided
with other amino acids in a mock seed-coat exudate. Arg as
the sole nitrogen source was converted to urea but did not support
cotyledon growth. There appeared to be a lack of recruitment of the
low-level arginase activity to hydrolyze free Arg in developing
embryos, thus avoiding a futile urea cycle.