[Verification of the peanut vitamin C synthesis-related gene AhPMM and its role in stress resistance].

Vitamin C plays an important role in plant antioxidation, photosynthesis, growth and development, and metabolism. In this study, a gene AhPMM, which is involved in vitamin C synthesis and responds significantly to low temperature, NaCl, polyethylene glycol (PEG) and abscisic acid (ABA) treatments, was cloned from peanut. An AhPMM overexpression vector was constructed, and transferred to a peanut variety Junanxiaohong using the pollen tube injection method. PCR test on the T3 generation transgenic peanut plants showed a transgenics positive rate of 42.3%. HPLC was used to determine the content of reducing vitamin C (AsA) and total vitamin C in the leaves of transgenic plants. The results showed that the content of AsA in some lines increased significantly, up to 1.90 times higher than that of the control, and the total vitamin content increased by up to 1.63 times compared to that of the control. NaCl and ABA tolerance tests were carried out on transgenic seeds. The results showed that the salt tolerance of transgenic seeds was significantly enhanced and the sensitivity to ABA was weakened compared to that of the non-transgenic control. Moreover, the salt tolerance of the transgenic plants was also significantly enhanced compared to that of the non-transgenic control. The above results showed that AhPMM gene not only increased the vitamin C content of peanut, but also increased the salt tolerance of transgenic peanut seeds and plants. This study may provide a genetic source for the molecular breeding of peanut for enhanced salt tolerance.

[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.

The Sweetpotato Voltage-Gated K+ Channel ß Subunit, KIbB1, Positively Regulates Low-K+ and High-Salinity Tolerance by Maintaining Ion Homeostasis.

Voltage-gated K+ channel ß subunits act as a structural component of Kin channels in different species. The ß subunits are not essential to the channel activity but confer different properties through binding the T1 domain or the C-terminal of α subunits. Here, we studied the physiological function of a novel gene, KIbB1, encoding a voltage-gated K+ channel ß subunit in sweetpotato. The transcriptional level of this gene was significantly higher in the low-K+-tolerant line than that in the low-K+-sensitive line under K+ deficiency conditions. In Arabidopsis, KIbB1 positively regulated low-K+ tolerance through regulating K+ uptake and translocation. Under high-salinity stress, the growth conditions of transgenic lines were obviously better than wild typr (WT). Enzymatic and non-enzymatic reactive oxygen species (ROS) scavenging were activated in transgenic plants. Accordingly, the malondialdehyde (MDA) content and the accumulation of ROS such as H2O2 and O2- were lower in transgenic lines under salt stress. It was also found that the overexpression of KIbB1 enhanced K+ uptake, but the translocation from root to shoot was not affected under salt stress. This demonstrates that KIbB1 acted as a positive regulator in high-salinity stress resistance through regulating Na+ and K+ uptake to maintain K+/Na+ homeostasis. These results collectively suggest that the mechanisms of KIbB1 in regulating K+ were somewhat different between low-K+ and high-salinity conditions.

Total synthesis of ailanthoidol and precursor XH14 by Stille coupling.

Ailanthoidol 1, which can be isolated from Chinese herbal medicine, is achieved in which the longest linear sequence is only six steps in 48% overall yield from commercially available 5-bromo-2-hydroxy-3-methoxybenzaldehyde. The key transformations in the synthesis are the Stille coupling reactions of benzofuranyl bromide with stannanyl compounds. This synthetic strategy can be modified to give access to a variety of different ailanthoidol and XH14 analogues.