Cyclic AMP deficiency negatively affects cell growth and enhances stress-related responses in tobacco Bright Yellow-2 cells

Abstract

Cyclic adenosine 3',5'-monophosphate (cAMP) is a recognized second messenger; however, knowledge of cAMP involvement in plant physiological processes originates primarily from pharmacological studies. To obtain direct evidence for cAMP function in plants, tobacco Bright Yellow-2 (BY-2) cells were transformed with the cAMP sponge, which is a genetically encoded tool that reduces cAMP availability. BY-2 cells expressing the cAMP sponge (cAS cells), showed low levels of free cAMP and exhibited growth inhibition that was not proportional to the cAMP sponge transcript level. Growth inhibition in cAS cells was closely related to the precocious inhibition of mitosis due to a delay in cell cycle progression. The cAMP deficiency also enhanced antioxidant systems. Remarkable changes occurred in the cAS proteomic profile compared with that of wild-type (WT) cells. Proteins involved in translation, cytoskeletal organization, and cell proliferation were down-regulated, whereas stress-related proteins were up-regulated in cAS cells. These results support the hypothesis that BY-2 cells sense cAMP deficiency as a stress condition. Finally, many proteasome subunits were differentially expressed in cAS cells compared with WT cells, indicating that cAMP signaling broadly affects protein degradation via the ubiquitin/proteasome pathway.

Genetic buffering of cyclic AMP in Arabidopsis thaliana compromises the plant immune response triggered by an avirulent strain of Pseudomonas syringae pv. tomato

“…At resting level (mock), H 2 O 2 content was higher in cAS than in WT plants, suggesting that the low levels of cAMP could be sensed as a stress condition, as already reported by Sabetta et al . (). However, in WT plants, a significant increase in H 2 O 2 content was observed at 4 hpi and this increased further at 24 hpi, whereas the H 2 O 2 increase in cAS plants occurred only 24 h after infection with avirulent bacteria, and at higher level compared with WT plants.…”

“…This strategy cannot therefore fully reveal cAMP‐dependent signalling mechanisms. Recently, a new genetic tool, namely the chimeric protein ‘cAMP‐sponge’, has been successfully used in plants, specifically in tobacco Bright Yellow‐2 cells, to study cAMP involvement in cell cycle progression and stress‐related mechanisms (Sabetta et al ., ). The cAMP‐sponge is constituted by the two‐high affinity cAMP‐binding domains of the human PKA Iβ regulatory subunit.…”

“…Advances in molecular studies and analytical methods for the detection, imaging and quantification of cNMPs have allowed definition of a more precise role for cAMP in plant growth and defence responses. Several studies have reported that cAMP has direct and/or indirect roles in many developmental plant processes, spanning from cell cycle (Ehsan et al ., ; Sabetta et al ., ) and pollen tube growth (Moutinho et al ., ) to stomata closure (Curvetto et al ., ; Newton and Smith, ) and ion homeostasis (Anderson et al ., ; Bolwell, ; Trewavas, ). More recently, through a proteomic approach, the involvement of cAMP‐mediated signalling has been reported in response to temperature and light stresses, and in the regulation of photosynthesis and photorespiration (Thomas et al ., ; Donaldson et al ., ).…”

The Mammalian Peptide Adrenomedullin Acts as a Growth Factor in Tobacco Plants

“…In mammals, AM growth-related actions are mediated by intracellular elevations of cAMP and activation of mitogen-activated protein kinase cascades, among others (Larrayoz et al, 2014). These pathways are also present in vascular plants and both of them regulate plant cell proliferation (Xu and Zhang, 2015; Sabetta et al, 2016). Cell cycle, both in animals and plants, is driven by several regulatory proteins designated as cyclins and their cyclin-dependent kinases (CDK), whose expression often depends on plant hormones, growth conditions, and developmental stages (Espinosa-Ruiz et al, 2004).…”

Interrogating cyclic AMP signaling using optical approaches

“…This construct has been used, for example, to elucidate functional roles for cAMP in stress signaling in plant cells [36] and to evaluate intercellular cAMP communication via gap junctions [35]. Averaimo and colleagues used a combination of targeted cAMP sponge and light-activated adenylyl cyclases to control cAMP levels in the vicinity of lipid rafts in retinal ganglion cells.…”