Methionine oxidation and reduction of the ethylene signaling component MaEIL9 are involved in banana fruit ripening

The ethylene insensitive 3/ethylene insensitive3-like(EIN3/EIL)plays an indispensable role in fruit ripening.However,the regulatory mechanism that links post-translational modification of EIN3/EIL to fruit ripening is largely unknown.Here,we studied the expression of 13 MaE IL genes during banana fruit ripening,among which MaE IL9 displayed higher enhancement particularly in the ripening stage.Consistent with its transcript pattern,abundance of MaE IL9 protein gradually increased during the ripening process,with maximal enhancement in the ripening.DNA affinity purification(DAP)-seq analysis revealed that MaE IL9 directly targets a subset of genes related to fruit ripening,such as the starch hydrolytic genes MaA MY3D and MaB AM1.Stably overexpressing MaE IL9 in tomato fruit hastened fruit ripening,whereas transiently silencing this gene in banana fruit retarded the ripening process,supporting a positive role of MaEIL9 in fruit ripening.Moreover,oxidation of methionines(Met-129,Met-130,and Met-282)in MaEIL9 resulted in the loss of its DNA-binding capacity and transcriptional activation activity.Importantly,we identified MaEIL9 as a potential substrate protein of methionine sulfoxide reductase A MaMsrA4,and oxidation of Met-129,Met-130,and Met-282in MaEIL9 could be restored by MaMsrA4.Collectively,our findings reveal a novel regulatory network controlling banana fruit ripening,which involves MaMsrA4-mediated redox regulation of the ethylene signaling component MaEIL9.

Kinetic studies of xylan hydrolysis of corn stover in a dilute acid cycle spray flow-through reactor

Xylan of corn stover was pretreated with 1%,2%and 3%(w/w)sulfuric acid at relatively low temperatures(90℃,95℃ and 100℃)in a dilute acid cycle sprayflow-through reactor(DCF).The hydrolysis of xylan to its monomeric xylose was modeled by a series offirst-order reactions.Both biphasic and Saeman hydrolysis models were applied tofit the experimental data.The results confirmed that the kinetic data of xylan hydrolysisfitted afirst-order irreversible reaction model and the experimental data.The reaction rates of xylose monomer formation and degradation were sensitive to catalyst concentration and temperature.Higher catalyst concentra-tion and lower reaction temperature result in high xylose yield.The activation energy for xylose formation and degradation were determined to be 112.9 and 101.0 kJ·mol^(-1),respectively.Over 90%theoretical xylose obtained from corn stover can be used to produce ethanol,xylitol and fumaric acid by fermentation.