Detalle de: Mammalian phosphodiesterase inhibitors reveal a role for cAMP in plant cell reprogramming toward embryogenesis in crop and forest species

Somatic embryogenesis is an example of plant cell totipotency and an essential tool for plant breeding and biotechnology, yet its low efficiency remains a major limitation in many species. Although 3', 5'-cyclic adenosine monophosphate (cAMP) is increasingly recognized as a signaling molecule in plants, its role in developmental cell reprogramming is unknown. Here, we investigated whether pharmacological modulation of cAMP homeostasis using small-molecule inhibitors of mammalian phosphodiesterases (PDEs) could increase the rate of cell reprogramming towards embryogenesis in plants. Four structurally diverse PDE inhibitors were evaluated in three embryogenesis systems: microspore embryogenesis of Brassica napus and Hordeum vulgare, and somatic embryogenesis of Quercus suber. PDE inhibitors quantitatively enhanced cell reprogramming and initiation of embryogenesis in all three species, whereas structurally-related inactive analogues did not. Biochemical analyses demonstrated that treatment with the representative PDE7 inhibitor TC2.43 significantly increased cAMP levels, providing functional evidence that PDE inhibition modulates cAMP homeostasis in plant embryogenic cultures. Increased cAMP level was accompanied by increased expression of key embryogenesis regulators (FUS3, LEC2 and SERK1-like) and auxin biosynthesis and signaling genes (TAA1/TAR2 and ARF5), suggesting that cAMP signaling would be integrated into the molecular network controlling embryogenic competence acquisition. These findings on three evolutionarily distant angiosperms, two crops and a forest tree, suggest that the embryogenesis-promoting effects of PDE inhibition would be conserved across diverse taxa. Moreover, they identify changes in cAMP levels as a new player in embryogenic induction and suggest mammalian PDE inhibitors as promising chemical additives for improving in vitro plant regeneration.