Abstract
Isoprene is the most abundant single biogenic volatile compound emitted by plants. Despite the relevance of this molecule to plant abiotic resistance and its impact on global atmospheric chemistry, little is known about the details of its mechanism of action. Here, we characterized through both physiological and molecular methods the mechanisms of action of isoprene using model transgenic arabidopsis lines overexpressing a monocot isoprene synthase gene. Our results demonstrated the effect that isoprene had on ABA signaling at different tissue-specific, spatial, and temporal scales. In particular, we found that isoprene enhanced stomatal sensitivity to ABA through upregulation of RD29B signaling gene. By contrast, isoprene decreased sensitivity to ABA in germinating seeds and roots, suggesting tissue-specific mechanisms of action. In leaves, isoprene caused the downregulation of COR15A and P5CS genes, suggesting that the enhanced tolerance to water-deprivation stress observed in isoprene-emitting plants may be mediated chiefly by an enhanced membrane integrity and tolerance to osmotic stress.
Highlights
Plants, as sessile organisms, have developed diverse defense mechanisms to allow them to adapt to sudden and severe environmental changes
It was estimated that around 70% of non-methane biogenic volatile compounds in the atmosphere annually are derived from isoprene emission alone at the global level [3]
Its emission is further stimulated when leaves are subjected to or recovering from environmental stresses [6,7,8,9]. These findings suggest that isoprene emission is capable of responding to many stresses and provides benefits to plants [5,10]
Summary
As sessile organisms, have developed diverse defense mechanisms to allow them to adapt to sudden and severe environmental changes. Drought (water deficiency) and heat (high temperature) are considered the most detrimental abiotic stresses, which cause severe damage to plant survival and crop production. It has been reported that isoprene (2-methyl-1,3-butadiene, a biogenic volatile compound) plays fundamental roles in protecting plants against oxidative stress under various environmentally unfavorable conditions [2]. Its emission is further stimulated when leaves are subjected to or recovering from environmental stresses [6,7,8,9]. Hypotheses about the protective mechanisms of isoprene emission to improve plant tolerance against biotic and abiotic stresses include membrane stabilization [11,12], direct reactions with reactive oxygen and nitrogen species [13,14,15], and indirect alteration of ROS signaling [2,16]. Vickers and colleagues proposed a unified mechanism by which the antioxidant behavior of isoprene improves a variety of abiotic stresses resistance in isoprene emitting plants [10]
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