Abstract
Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS) have been proposed as universal signaling molecules in plant stress responses. There are a growing number of studies suggesting that hydrogen sulfide (H2S) or Reactive Sulfur Species (RSS) are also involved in plant abiotic as well as biotic stress responses. However, it is still a matter of debate as to how plants utilize those RSS in their signaling cascades. Here, we demonstrate that d-cysteine is a novel candidate for bridging our gap in understanding. In the genus of the tiny water-floating fern Azolla, a rapid root abscission occurs in response to a wide variety of environmental stimuli as well as chemical inducers. We tested five H2S chemical donors, Na2S, GYY4137, 5a, 8l, and 8o, and found that 5a showed a significant abscission activity. Root abscission also occurred with the polysulfides Na2S2, Na2S3, and Na2S4. Rapid root abscission comparable to other known chemical inducers was observed in the presence of d-cysteine, whereas l-cysteine showed no effect. We suggest that d-cysteine is a physiologically relevant substrate to induce root abscission in the water fern Azolla.
Highlights
Plants sense environmental conditions and transmit the environmental signals to regulate their growth and development
H2 S study, we suggest here the application of the water-floating fern Azolla, a good model plant to explore the physiological functions of chemical compounds [19,20,21]
The present study has demonstrated that d-cysteine is a good inducer of rapid root abscission in A. pinnata (Figures 6 and 7), a novel finding that provides an important clue to reveal the root abscission mechanism. d-amino acids had long been thought as a laboratory artifact
Summary
Plants sense environmental conditions and transmit the environmental signals to regulate their growth and development. Stomatal movement is one of the rapid responses of plants, both opening and closure movements finish within an hour [2]. The potential for cross talk between ROS and RNS has become a subject of debate regarding the signaling mechanism in guard cells [8,9]. In this century, Reactive Sulfur Species (RSS) was hypothesized as the third group of redox-active molecular species that may be associated with oxidative stress [1,10,11]. There is an increasing number of reports suggesting regulatory functions of H2 S or RSS in cellular signaling mechanisms [12]
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