EgSPEECHLESS and its putative binding targets are involved in the salt response of oil palm

Oil palm is the most productive oil producing plant. Salt stress leads to growth damage and decrease in yield of oil palm. However, the physiological responses of oil palm to salt stress and their underlying mechanisms are not clear. RNA-Seq for leaf samples from young palms challenged under three levels of salts (100, 250 and 500 mM NaCl) for 14 days and control was conducted. All the three levels of salt stress activated EgSPCH expression and increased stomatal density of oil palm. ~ 41% of DEGs were putative EgSPCH binding target and were involved in multiple bioprocesses related to salt response. Overexpression of EgSPCH in Arabidopsis increased the stomatal production and lowered the salt tolerance. These data indicate that in oil palm, salt activates EgSPCH to generate more stomata in response to salt stress, which is different with that in herbaceous plants. Our results might mirror the difference of salt-induced stomatal development between ligneous and herbaceous crops.