miR164g-MsNAC022 acts as a novel module mediating drought response by transcriptional regulation of reactive oxygen species scavenging systems in apple.

Under drought stress, reactive oxygen species (ROS) overaccumulate as a secondary stress that impairs plant performance and thus severely reduces crop yields. The mitigation of ROS levels under drought stress is therefore crucial for drought tolerance. MicroRNAs (miRNAs) are critical regulators of plant development and stress responses. However, the complex molecular regulatory mechanism by which they function during drought stress, especially in drought-triggered ROS scavenging, is not fully understood. Here, we report a newly identified drought-responsive miRNA, miR164g, in the wild apple species Malus sieversii and elucidate its role in apple drought tolerance. Our results showed that expression of miR164g is significantly inhibited under drought stress and it can specifically cleave transcripts of the transcription factor MsNAC022 in M. sieversii. The heterologous accumulation of miR164g in Arabidopsis thaliana results in enhanced sensitivity to drought stress, while overexpression of MsNAC022 in Arabidopsis and the cultivated apple line 'GL-3' (Malus domestica Borkh.) lead to enhanced tolerance to drought stress by raising the ROS scavenging enzymes activity and related genes expression levels, particularly PEROXIDASE (MsPOD). Furthermore, we showed that expression of MsPOD is activated by MsNAC022 in transient assays. Interestingly, Part1 (P1) region is the key region for the positive regulation of MsPOD promoter by MsNAC022, and the different POD expression patterns in M. sieversii and M. domestica is attributed to the specific fragments inserted in P1 region of M. sieversii. Our findings reveal the function of the miR164g-MsNAC022 module in mediating the drought response of M. sieversii and lay a foundation for breeding drought-tolerant apple cultivars.

[Experimental study on treatment of immune ulcerative colitis in mice by Changlu Enema].

OBJECTIVE: To observe the therapeutic effect of Chinese compound, Changlu Enema (CE), on immune ulcerative colitis (UC) in mice. METHODS: Mice were randomly divided into the normal group, the model group, the CE high dose (CE-H) and low dose (CE-L) group and the salicylazosulfapyridine (SASP) group. All mice, except those in the normal group, were made into UC model by colonic mucosa protein immunization. After 21 days of medication, the changes of UC activity index and body weight in mice were observed, and the condition of colonic inflammation and histomorphological changes in colonic tissue were observed also. RESULTS: UC activity index was lower and body weight was higher in the two CE groups than those in the model group respectively, showing significant difference (P < 0.05 or P < 0.01); pathological examination showed the pathological changes and inflammatory response in colonic tissue were relieved significantly after treatment, and the improvement in the CE-H group was better than that in the SASP group. CONCLUSION: TCM compound CE is markedly effective in treating UC rats.