Diadenosine polyphosphates (Ap₃A and Ap₄A) behave as alarmones triggering the synthesis of enzymes of the phenylpropanoid pathway in Arabidopsis thaliana

Abstract

It is known that cells under stress accumulate various dinucleoside polyphosphates, compounds suggested to function as alarmones. In plants, the phenylpropanoid pathways yield metabolites protecting these organisms against various types of stress. Observations reported in this communication link these two phenomena and provide an example of a metabolic “addressee” for an “alarm” signaled by diadenosine triphosphate (Ap3A) or diadenosine tetraphosphate (Ap4A). In response to added Ap3A or Ap4A, seedlings of Arabidopsis thaliana incubated in full nutrition medium increased both the expression of the genes for and the specific activity of phenylalanine ammonia-lyase and 4-coumarate:coenzyme A ligase, enzymes that control the beginning of the phenylpropanoid pathway. Neither adenine mononucleotides (AMP, ADP or ATP) nor adenosine evoked such effects. Reactions catalyzed in vitro by these enzymes were not affected by Ap3A or Ap4A.

Exogenous adenosine 5′-phosphoramidate behaves as a signal molecule in plants; it augments metabolism of phenylpropanoids and salicylic acid in Arabidopsis thaliana seedlings

“…The gene-stimulatory effects exerted by these nucleotides were similar to effects observed earlier for 4CL and CHS in response to exogenous ApppA or AppppA. Interestingly, each of these two dinucleotides evoked a dramatic, >70-fold increase in PAL2 expression (Pietrowska-Borek et al, 2011). In the experiments with NH 2 -pA or F-pA none of the three PALs was stimulated more than 2e3-fold, and PAL4 was hardly stimulated relative to the controls.…”

“…Plants (100e120 seedlings) were grown in sterile liquid culture in orbital shakers in 250-mL Erlenmeyer flasks containing 30 mL full nutrition media according to Scheible et al (2004). The experiments were carried out as described by Pietrowska-Borek et al (2011). Adenosine 5 0 -monophoshoramidate, NH 2 -pA, (Sigma, St. Louis, MO, USA) and adenosine 5 0 -monophosphofluoride, F-pA, synthesized according to Wittman (1963), were added at 5 mM final concentration to 7-day-old seedlings.…”

“…Bandurska and Cie slak, 2013). (5) In our earlier studies, we showed that micromolar concentrations of exogenous ApppA or AppppA (Pietrowska-Borek et al, 2011) and 8-Br-cAMP or 8-Br-cGMP (believed to act like the parent cyclic nucleotides) , behaved as signaling molecules (alarmones) when added to seedlings of Arabidopsis thaliana incubated in full nutrition medium. They markedly increased both the expression of the genes for and the specific activity of phenylalanine ammonia lyase (EC 4.3.1.5) and 4-coumarate:coenzyme A ligase (EC 6.2.1.12).…”

“…Although it is not yet known what factors affect the accumulation of NH 2 -pA in cells and whether its concentration may be increased by stress, we wondered if this rare nucleotide exerts any biochemical effect; functioning for example as a signal molecule. To test this, we carried out the same type of experiments that were performed with ApppA, AppppA (Pietrowska-Borek et al, 2011, 2014a and the cyclic nucleotides (Pietrowska-Borek and Nuc, 2013) mentioned above. We found that exogenous NH 2 -pA added to A. thaliana seedlings activated genes encoding proteins involved in the catalysis of six key reactions of the phenylpropanoid pathways and caused accumulation of compounds such as lignins, anthocyanins and salicylic acid (Fig.…”

Diadenosine 5′, 5′′′-P1,P4-tetraphosphate (Ap4A) is synthesized in response to DNA damage and inhibits the initiation of DNA replication

“…1a) is synthesized in prokaryotes and eukaryotes in response to a variety of cellular stresses and stimuli and has been described as a pleiotropically acting alarmone with a role in establishing the response to these stresses, although few molecular details of its actions have ever been established [1][2][3][4]. Thus, Ap4A has been implicated in the heat shock and DNA damage responses [5][6][7], apoptosis [8,9] and in several signalling pathways [10][11][12][13].…”