Self-Incompatibility Involved in the Level of Acetylcholine and cAMP

Abstract

Elongation of pollen tubes in pistils after self-pollination of Lilium longiflorum cv. Hinomoto exhibiting strong gametophytic self-incompatibility was promoted by cAMP and also promoted by some metabolic modulators, namely, activators (forskolin and cholera toxin) of adenylate cyclase and inhibitors (3-isobutyl-1-methylxanthine and pertussis) of cyclic nucleotide phosphodiesterase. Moreover, the elongation was promoted by acetylcholine (ACh) and other choline derivatives, such as acetylthiocholine, L-alpha-phosphatidylcholine and chlorocholinechloride [CCC; (2-chloroethyl) trimethyl ammonium chloride]. A potent inhibitor (neostigmine) of acetylcholinesterase (AChE) as well as acetylcholine also promoted the elongation. cAMP enhanced choline acetyltransferase (ChAT) activity and suppressed AChE activity in the pistils, suggesting that the results are closely correlated with self-incompatibility in L. longiflorum. In short, it came to light that cAMP modulates ChAT (acetylcholine-forming enzyme) and AChE (acetylchoine-decomposing enzyme) activities to enhance the level of ACh in the pistils of L. logiflorum after self-incompatible pollination. These results indicate that the self-incompatibility on self-pollination is caused by low levels of ACh and/or cAMP.

Cyclic AMP: A Polyhedral Signalling Molecule in Plants

“…Successively, it was demonstrated that cAMP stimulated the activity of choline acetyltransferase, which controls the synthesis of acetylcholine, a molecule that, together with other choline derivatives, promotes the elongation of Lilium longiflorum pollen tube. Thus, the low levels of cAMP and the subsequent low activity of choline acetyltransferase caused the self-incompatibility in Lilium longiflorum [ 58 ].…”

“… cAMP involvement in plant physiological processes. Literature data indicate a role for cAMP in ion homeostasis, mainly through the regulation of membrane-localised ion channels [ 29 , 34 , 35 , 36 , 40 , 48 , 49 , 50 , 51 , 52 , 53 , 54 ] and in stomatal opening, through Ca 2+ and K + flux regulation [ 39 , 40 , 52 , 53 ], cAMP was also shown to influence pollen tube orientation and growth, by the regulation of Ca 2+ channels and choline acetyltransferase activity [ 14 , 54 , 55 , 56 , 57 , 58 ]. Seed germination [ 59 , 60 , 61 , 62 , 63 ] and cell cycle progression [ 32 , 33 , 37 , 38 , 64 ] are also regulated by cAMP.…”

Acetylcholine promotes the emergence and elongation of lateral roots ofRaphanus sativus

“…Hinomoto after self-incompatible pollination. 1,2 Since Ewins 3 provided evidence for the existence of ACh in ergot (Claviceps purpurea) as well as animals, the existence of Ach in higher plants was first reported in a nettle (Urtica urens) grown in the Himalaya Mountains by Emmelin and Feldberg. 4 Hoshino 5 confirmed the existence of Ach in Vigna seedlings by mass spectrometry.…”