Effects Of CO₂ Concentration On Growth And Physiology Of Auricularia Heimuer

Auricularia heimuer is an indispensable delicacy on modern dining tables,and its demand and production are increasing year by year.With the continuous development of its cultivation techniques,the shed hanging bag cultivation model has gradually replaced the traditional basswood culture and ground pendulum culture.However,it is found in actual production that when the ventilation of the shed is poor,it will cause the CO₂concentration in the shed to increase.At this time,the ear pieces will have problems such as deformity and decline in stress resistance.However,the specific factors leading to the morphological changes and poor quality of A.heimuer are still unclear.Therefore,in this study,we established an A.heimuer culture device to study the effects of elevated CO₂concentration on the growth and related physiological characteristics of A.heimuer by setting different concentration gradients of CO₂,and explored the mechanism of CO₂concentration changes on the growth and development of A.heimuer using transcriptome analysis.The main research results are as follows:（1）Through the observation of culture of A.heimuer under different CO₂concentrations,it was found that the increase of CO₂concentration could promote the formation of A.heimuer primordium.With the extension of culture time,the physical morphology of A.heimuer significantly changed under high CO₂concentration,and a large number of deformed fruiting bodies appeared,which seriously affected the commodity value of fruiting bodies.（2）The activities of extracellular enzymes in mycelium,which tended to increase at fruitbody stage,were affected by elevated CO₂concentration.The activities of extracellular carboxy methylcellulase,filter paper cellulase and amylase were promoted when the CO₂concentration was between 0.22%-0.49%before the ear bud stage.With the increase of incubation time,the activities of these three enzymes were inhibited.The activities of antioxidant enzymes,the content of intermediate metabolites,and the activities of tricarboxylic acid cycle related enzymes in fruit bodies were significantly affected by elevated CO₂concentration.At the CO₂concentration of 0.22%-1.37%,the activities of SOD and CAT were increased,while the activities of NADP-malate dehydrogenase and NADP-isocitrate dehydrogenase were inhibited.By measuring the polysaccharide content in the seeds at the extension stage of ear piece,it was found that the increase of CO₂concentration was not conducive to the synthesis of polysaccharide.When the CO₂concentration was 1.37%,the polysaccharide content was only 54%of the control.（3）Through transcriptome sequencing analysis,it was found that the metabolism pathway of starch and sucrose as well as the tricarboxylic acid cycle pathway were significantly inhibited when CO₂concentration increased,which may be because the high CO₂concentration made the fruity body of A.heimuer breathe poorly,resulting in the decline of its metabolism,and thus the change of the growth and development process of the fruity body.The differential genes were analyzed,and two carbonic anhydrase genes were found to be the key genes controlling the morphology of A.heimuer.Three heat shock protein genes were significantly affected by CO₂concentration,which might be the key genes in response to CO₂concentration changes in the fruit body of A.heimuer.