Ethylene biosynthesis and signaling in rice
Guillaume Rzewuski and Margret Sauter
Plant Science, Volume 175, Issues 1-2, July-August 2008, Pages 32-42
2008
บทคัดย่อ
Ethylene accumulates to higher levels upon submergence of rice plants where it plays a central role in hypoxia adaptation. In deepwater rice positive feedback regulation of ethylene on the biosynthetic genes 1-aminocyclopropane-1-carboxylic acid synthase (OsACS5), ACC oxidase (OsACO1 and OsACO3) and the Yang cycle OsARD1 gene likely contributes to maintain elevated rates of ethylene synthesis over prolonged periods of time. Ethylene modulates gibberellin and abscisic acid homeostasis thereby promoting internodal growth which keeps part of the foliage above flood waters. Ethylene further induces growth of adventitious roots and programmed cell death to form aerenchyma and to facilitate adventitious root emergence at stem nodes. The ethylene signaling components identified so far in rice include receptors, an EIN2 and an EIN3 ortholog, and CTR1, RTE1, EBF1/2 and EIN5 homologs that are conserved between the dicot Arabidopsis and the monocot rice. Based on the observation that ein2 and eil1 mutants of rice do not display a strong phenotype we conclude that ethylene signaling in rice may be more intricate than in Arabidopsis. In addition, ethylene may have specific signaling outputs in semiaquatic plants such as rice as was shown for Yang cycle regulation. Functional analysis of signaling pathways including the large ethylene response factor (ERF) family may help understand how ethylene co-ordinates adaptive responses to flooding stress in rice.