IFEVA   02662
INSTITUTO DE INVESTIGACIONES FISIOLOGICAS Y ECOLOGICAS VINCULADAS A LA AGRICULTURA
Unidad Ejecutora - UE
artículos
Título:
Seed Dormancy and GA Metabolism in Sorghum.
Autor/es:
RODRIGUEZ MV, MENDIONDO GM, CANTORO R, AUGE G, LUNA V, MASCIARELLI O, BENECH-ARNOLD RL.
Revista:
PLANT AND CELL PHYSIOLOGY
Editorial:
OXFORD UNIV PRESS
Referencias:
Año: 2012 vol. 53 p. 64 - 80
ISSN:
0032-0781
Resumen:
Grain sorghum [Sorghum bicolor (L) moench] exhibits
intraspecific variability for the rate of dormancy release and
pre-harvest sprouting behavior. Two inbred
lines with contrasting sprouting response were
compared: IS9530 (resistant) and RedlandB2 (susceptible). Precocious
dormancy
release in RedlandB2 is related to an early loss of
embryo sensitivity to ABA and higher levels of gibberellins in imbibed
grains as compared with IS9530. With the aim of
identifying potential regulatory sites for gibberellin metabolism
involved
in the expression of dormancy in immature grains of
both lines, we carried out a time course analysis of transcript levels
of putative gibberellin metabolism genes and
hormone content (GA1, GA4, GA8 and GA34). A lower embryonic GA4 level in dormant IS9530 was related to a sharp and transient induction of two SbGA2-oxidase (inactivation) genes. In contrast, these genes were not induced in less dormant RedlandB2, while expression of two SbGA20-oxidase (synthesis) genes increased together with active GA4 levels before radicle protrusion. Embryonic levels of GA4 and its catabolite GA34 correlated negatively. Thus, in addition to the process of gibberellin synthesis, inactivation is also important in regulating
GA4 levels in immature grains. A negative regulation by gibberellins was observed for SbGA20ox2, SbGA2ox1 and SbGA2ox3 and also for SbGID1
encoding a gibberellin receptor. We propose that the coordinated
regulation at the transcriptional level of several gibberellin
metabolism genes identified in this work affects
the balance between gibberellin synthesis and inactivation processes,
controlling
active GA4 levels during the expression of dormancy in maturing sorghum grains.