A rapid alkalinization factor-like peptide EaF82 impairs tapetum degeneration during pollen development

In plants, many small peptides have been discovered and are thought to function as growth regulators. However, the functions of most of them remain unknown. In this study, we systematically characterized EaF82, a novel cysteine-rich peptide isolated from shy-flowering ‘Golden Pothos’ plants. Our studies revealed that EaF82 is closely related to the rapid alkalinization factors (RALFs) and displays alkalinizing activity. Its heterologous expression in Arabidopsis impaired tapetum degeneration and reduced pollen production and seed yields. RNA-Seq, RT-qPCR and biochemical analyses showed that overexpressing EaF82 down-regulated a group of genes involved in pH changes, cell wall modifications, tapetum degeneration and pollen maturation as well as endogenous Arabidopsis clade IV AtRALFs, and decreased proteasome activity and ATP levels. Yeast two-hybrid screening and co-immunoprecipitation identified AKIN10, an energy sensing kinase, to be its interacting partner. These results suggest that EaF82 action may be mediated through AKIN10 leading to alterations of transcriptome and energy metabolism, thereby causing ATP deficiency and impairing pollen development. Our study reveals a new regulatory role for RALF peptide in tapetum degeneration.