[Analysis of the salt-stress responsive element of the promoter of peanut small GTP binding protein gene AhRabG3f].

To study the molecular mechanism of salt stress response of peanut small GTP binding protein gene AhRabG3f, a 1 914 bp promoter fragment upstream of the start codon of AhRabG3f gene (3f-P) from peanut was cloned. Subsequently, five truncated fragments (3f-P1-3f-P5) with lengths of 1 729, 1 379, 666, 510 and 179 bp were obtained through deletion at the 5' end, respectively. Plant expression vectors where these six promoter fragments were fused with the gus gene were constructed and transformed into tobacco by Agrobacterium-mediated method, respectively. GUS expression in transgenic tobacco and activity analysis were conducted. The gus gene expression can be detected in the transgenic tobacco harboring each promoter segment, among which the driving activity of the full-length promoter 3f-P was the weakest, while the driving activity of the promoter segment 3f-P3 was the strongest. Upon exposure of the transgenic tobacco to salt stress, the GUS activity driven by 3f-P, 3f-P1, 3f-P2 and 3f-P3 was 3.3, 1.2, 1.9 and 1.2 times compared to that of the transgenic plants without salt treatment. This suggests that the AhRabG3f promoter was salt-inducible and there might be positive regulatory elements between 3f-P and 3f-P3 in response to salt stress. The results of GUS activity driven by promoter fragments after salt treatment showed that elements included MYB and GT1 between 1 930 bp and 1 745 bp. Moreover, a TC-rich repeat between 682 bp and 526 bp might be positive cis-elements responsible for salt stress, and an MYC element between 1 395 bp and 682 bp might be a negative cis-element responsible for salt stress. This study may facilitate using the induced promoter to regulate the salt resistance of peanut.

Close association between the synergistic toxicity of zearalenone-deoxynivalenol combination and microRNA221-mediated PTEN/PI3K/AKT signaling in HepG2 cells.

Mycotoxins can impart different types of combined toxicity to humans and animals, therefore, it is critical to understand the underlying mechanisms to eliminate the harm. Herein a combination of zearalenone (ZEA) at 2 µM and deoxynivalenol (DON) at 0.1 µM decreased cell viability and increased ROS level in HepG2 cells, suggesting synergistic toxicity exerted by ZEA and DON even at their low toxic concentrations. Moreover, apoptosis and inflammatory response were promoted after the co-exposure of ZEA and DON, indicated by the increased expression of BAX, Caspase-3, IL-1ß and IL-6 genes. Such synergistic toxicity was closely associated with miR-221-mediated PTEN/PI3K/AKT signal pathway, with a negative regulatory relationship between PTEN and PI3K/AKT signaling. MiR-221 could influence cell viability and ROS level to counter the combined toxicity of ZEA and DON through targeting directly PTEN gene. This study demonstrated the toxicological impact of mycotoxin interactions on cells, and critical role of the interplay between miRNAs and PTEN in monitoring the synergistic toxicity of mycotoxin mixture.