Reference "Ethylene promotes submergence-induced expression of OsABA8ox1, a gene that encodes ABA 8'-hydroxylase in rice"

Reference ID

11448

Title

Ethylene promotes submergence-induced expression of OsABA8ox1, a gene that encodes ABA 8'-hydroxylase in rice

Source

Plant & cell physiology, 2007, vol. , pp. -

Authors (17)

Saika-H	Okamoto-M	Miyoshi-K	Kushiro-T	Shinoda-S
Jikumaru-Y	Fujimoto-M	Arikawa-T	Takahashi-H	Ando-M
Arimura-S-I	Miyao-A	Hirochika-H	Kamiya-Y	Tsutsumi-N
Nambara-E	Nakazono-M

Abstract

A rapid decrease of the plant hormone abscisic acid (ABA) under submergence is
thought be a prerequisite for the enhanced elongation of submerged shoots of
rice (Oryza sativa L.). Here, we report that the level of phaseic acid (PA), an
oxidized form of ABA, increased with decreasing ABA level during submergence.
The oxidation of ABA to PA is catalyzed by ABA 8'-hydroxylase, which is possibly
encoded by three genes (OsABA8ox1, -2 and -3) in rice. The ABA 8'-hydroxylase
activity was confirmed in microsomes from yeast expressing OsABA8ox1. OsABA8ox1-
GFP fusion protein in onion cells was localized to the endoplasmic reticulum.
The mRNA level of OsABA8ox1, but not the mRNA levels of other OsABA8ox genes,
increased dramatically within 1 h after submergence. On the other hand, the mRNA
levels of genes involved in ABA biosynthesis (OsZEP and OsNCEDs) decreased after
1-2 h of submergence. Treatment of aerobic seedlings with ethylene and its
precursor, 1-aminocyclopropane-1-carboxylate (ACC), rapidly induced the
expression of OsABA8ox1, but the ethylene treatment did not strongly affect the
expression of ABA biosynthetic genes. Moreover, pretreatment with 1-
methylcyclopropene (1-MCP), a potent inhibitor of ethylene action, partially
suppressed induction of OsABA8ox1 expression under submergence. The ABA level
was found to be negatively correlated with OsABA8ox1 expression under ACC or 1-
MCP treatment. Together, these results indicate that the rapid decrease in ABA
levels in submerged rice shoots is controlled partly by ethylene-induced
expression of OsABA8ox1 and partly by ethylene-independent suppression of genes
involved in the biosynthesis of ABA.