Ethylene signaling modulates tomato pollen tube growth, through modifications of cell wall remodeling and calcium gradient
Résumé
Ethylene modulates plant developmental processes including flower development. Previous studies have suggested ethylene participation in pollen tube (PT) elongation, and both ethylene production and perception seem critical at fertilization time. The full gene set regulated by ethylene during PT growth is unknown. To study this, we used various EThylene Receptors (ETRs) tomato mutants: etr3-ko, a loss-of-function (LOF) mutant; and NR (Never Ripe), a gain of function (GOF) mutant. The etr3-ko PTs grew faster than its wild type, WT. Oppositely, NR PT elongation was slower than its wild type, and PTs displayed larger diameters. ETR mutations created feedbacks on ethylene production. Furthermore, the ethylene treatment of germinating pollen grains increased PT length in etr-ko mutants and WT, but not in NR. Treatments with the ethylene perception inhibitor, 1-MCP, decreased PT length in etr-ko mutants and wild types, but had no effect on NR. This confirmed that ethylene regulates PT growth. The comparison of PT transcriptomes in LOF and GOF mutants, etr3-ko and NR, both mutated on the ETR3 gene, revealed that ethylene perception has major impacts on cell wall- and calcium-related genes as confirmed by microscopic observations showing a modified distribution of the methylesterified homogalacturonan pectic motif and of calcium load. Our results establish links between PT growth, ethylene, calcium and cell wall metabolisms, and also constitute a transcriptomic resource.
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