Abstract
In higher plants under low oxygen or hypoxic conditions, the phytohormone ethylene and hydrogen peroxide (H2O2) are involved in complex regulatory mechanisms in hypoxia signaling pathways. The respiratory burst oxidase homolog D (RbohD), an NADPH oxidase, is involved in the primary stages of hypoxia signaling, modulating the expression of downstream hypoxia-inducible genes under hypoxic stress. In this study, our data revealed that under normoxic conditions, seed germination was delayed in the rbohD/ein2-5 double mutant, whereas postgermination stage root growth was promoted. Under submergence, the rbohD/ein2-5 double mutant line had an inhibited root growth phenotype. Furthermore, chlorophyll content and leaf survival were reduced in the rbohD/ein2-5 double mutant compared with wild-type plants under submerged conditions. In quantitative RT-PCR analysis, the induction of Ethylene-responsive factor 73/hypoxia responsive 1 (AtERF73/HRE1) and alcohol dehydrogenase 1 (AtADH1) transcripts was lower in the rbohD/ein2-5 double mutant during hypoxic stress than in wild-type plants and in rbohD and ein2-5 mutant lines. Taken together, our results indicate that an interplay of ethylene and RbohD is involved in regulating seed germination and post-germination stages under normoxic conditions. Moreover, ethylene and RbohD are involved in modulating seedling root growth, leaf chlorophyll content, and hypoxia-inducible gene expression under hypoxic conditions.
Highlights
Climate change—induced flooding is a major global natural disaster
Our results demonstrate that the interplay between ethylene and H2 O2 is involved in modulating seed germination, seedling root growth, leaf chlorophyll content, and hypoxia-inducible gene expression under hypoxic conditions
To further investigate the interplay of ethylene and H2 O2 signaling during hypoxia, we obtained rbohD/ein2-5 double mutant lines by crossing single rbohD and ein2-5 homozygous mutants
Summary
Flooding and heavy rain can cause soil compaction, reducing soil oxygen concentration and resulting in hypoxic stress—induced plant damage. The plant hormone ethylene participates in regulating stress-inducible genes to help plants to adapt to various environmental stresses, especially in hypoxia signaling caused by flooding [1,2,3]. Ethylene controls diverse physiological pathways involved in plant growth and developmental processes including the regulation of seed germination and leaf senescence and the promotion of pollen tube growth and fruit ripening [4,5,6]. Ethylene contributes to plant responses to different biotic and abiotic stresses such as insect or microbial infections, drought, and salt conditions [7,8,9]. Several studies have shown that the ER-located membrane protein ETHYLENE INSENSITIVE 2 (EIN2)
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