Distinct endocytic pathways identified in tobacco pollen tubes using charged nanogold.
In an attempt to dissect endocytosis in Nicotiana tabacum L. pollen tubes, two different probes--positively or negatively charged nanogold--were employed. The destiny of internalized plasma membrane domains, carrying negatively or positively charged residues, was followed at the ultrastructural level and revealed distinct endocytic pathways. Time-course experiments and electron microscopy showed internalization of subapical plasma-membrane domains that were mainly recycled to the secretory pathway through the Golgi apparatus and a second mainly degradative pathway involving plasma membrane retrieval at the tip. In vivo time-lapse experiments using FM4-64 combined with quantitative analysis confirmed the existence of distinct internalization regions. Ikarugamycin, an inhibitor of clathrin-dependent endocytosis, allowed us to further dissect the endocytic process: electron microscopy and time-lapse studies suggested that clathrin-dependent endocytosis occurs in the tip and subapical regions, because recycling of positively charged nanogold to the Golgi bodies and the consignment of negatively charged nanogold to vacuoles were affected. However, intact positively charged-nanogold transport to vacuoles supports the idea that an endocytic pathway that does not require clathrin is also present in pollen tubes.
Moscatelli
Alessandra
A
Dipartimento di Biologia L. Gorini, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy. alessandra.moscatelli@unimi.it
Ciampolini
Fabrizio
F
Rodighiero
Simona
S
Onelli
Elisabetta
E
Cresti
Mauro
M
Santo
Nadia
N
Idilli
Aurora
A
D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D033922:Clathrin Heavy Chains / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D005456:Fluorescent Dyes / Q000378:metabolism; D006046:Gold / Q000737:chemistry / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D007769:Lactams / Q000378:metabolism; D054118:Nanospheres / Q000737:chemistry; D053205:Pollen Tube / Q000378:metabolism / Q000648:ultrastructure*; D011726:Pyridinium Compounds / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D014026:Nicotiana / Q000166:cytology / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism / Q000648:ultrastructure
C092350:FM 4-64; D005456:Fluorescent Dyes; D007769:Lactams; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D033922:Clathrin Heavy Chains; C074292:ikarugamycin; D006046:Gold