Drought and re-watering modify ethylene production and sensitivity, and
are associated with coffee anthesis
Abstract
Coffee flowering requires a period of water deficit followed by rainfall
to break flower bud dormancy and promote anthesis. Since drought
followed by re-watering can increase shoot ethylene production, we
investigated changes in root, leaf and flower bud ethylene production
and expression of genes within the ethylene biosynthesis and signalling
pathways and their relationship to coffee flowering. Drought decreased
foliar and flower bud ethylene production without changing root ethylene
production, even though all tissues likely accumulated the ethylene
precursor ACC (1-aminocyclopropane-1-carboxylic acid), since ACS gene
expression was maintained while ACO gene expression decreased. The
ethylene receptor CaETR4-like was not differentially expressed in leaves
under water deficit, but it was downregulated in roots. Re-watering
restored shoot ethylene production, which seems important in promoting
anthesis. 1-MCP, an ethylene action inhibitor, triggered coffee anthesis
without re-watering the plants, which hitherto was considered essential
to allow flowering. 1-MCP positively regulated ethylene biosynthesis
genes (CaACS1-like and CaACO1-like), similar to re-watering, and
downregulated CaETR4-like, suggesting that changes in ethylene levels
and sensitivity are required to promote coffee anthesis. Thus, drought
and re-watering-induced changes in ethylene levels and sensitivity allow
coffee flowering, while the growth regulator 1-MCP can potentially
regulate anthesis time and intensity.