title: Natural polyamines and synthetic analogs modify the growth and the morphology of Pyrus communis pollen tubes affecting ROS levels and causing cell death.
abstract: Polyamines (PAs) are small molecules necessary for pollen maturation and tube growth. Their role is often controversial, since they may act as pro-survival factors as well as factors promoting Programmed Cell Death (PCD). The aim of the present work was to evaluate the effect of exogenous PAs on the apical growth of pear (Pyrus communis) pollen tube and to understand if PAs and reactive oxygen species (ROS) are interconnected in the process of tip-growth. In the present study besides natural PAs, also aryl-substituted spermine and methoctramine (Met 6-8-6) analogs were tested. Among the natural PAs, Spm showed strongest effects on tube growth. Spm entered through the pollen tube tip, then diffused in the sub-apical region that underwent drastic morphological changes, showing enlarged tip. Analogs were mostly less efficient than natural PAs but BD23, an asymmetric synthetic PAs bearing a pyridine ring, showed similar effects. These effects were related to the ability of PAs to cause the decrease of ROS level in the apical zone, leading to cell death, counteracted by the caspase-3 inhibitor Ac-DEVD-CHO (DEVD). In conclusions, ROS are essential for pollen germination and a strict correlation between ROS regulation and PA concentration is reported. Moreover, an imbalance between ROS and PAs can be detrimental thereby driving pollen toward cell death.
authors.affiliation: Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Alma Mater Studiorum-Università di Bologna, Via Irnerio 42, Bologna, Italy.
authors.forename: Iris
authors.initials: I
authors.lastname: Aloisi
authors.affiliation: Dipartimento di Scienze della Vita, Università di Siena, Via Mattioli 4, Siena, Italy.
authors.forename: Giampiero
authors.initials: G
authors.lastname: Cai
authors.affiliation: Dipartimento di Scienze per la Qualità della Vita, Alma Mater Studiorum-Università di Bologna, Corso d'Augusto 25, Rimini, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Tumiatti
authors.affiliation: Dipartimento di Farmacia e Biotecnologie, Alma Mater Studiorum-Università di Bologna, Via Belmeloro 6, Bologna, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Minarini
authors.affiliation: Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Alma Mater Studiorum-Università di Bologna, Via Irnerio 42, Bologna, Italy. Electronic address: stefano.delduca@unibo.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Del Duca
mesh_terms: D016923:Cell Death; D053205:Pollen Tube / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D011073:Polyamines / Q000378:metabolism*; D031989:Pyrus / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D011073:Polyamines; D017382:Reactive Oxygen Species
keywords: Cell death; DNA degradation; Pollen tube elongation; Polyamines; Pyrus communis L.; Reactive oxygen species