[Determination of trace elements in different parts of grapefruit by ICP-AES].

In the present paper, a method of simultaneous determination of trace elements in grapefruit was developed by using inductively coupled plasma-atomic emission spectrometry together with HNO3-HClO4 digestion. The contents of fifteen elements, including B, Ba, Ca, Cu, Zn, Mg, Sr, Mn, Fe, Na, Be, Pb, Bi, Cd and As, were determined in four parts, namely flesh, scarfskin, endodermis and seed collected from Guangdong, Guangxi and Ganzhou, respectively. The relative standard deviations for all these elements in this method were between 0.22% and 5.54%, and the recovery rates were between 87.0% and 115.0%. The measuring method was proved to be simple, rapid, reliable, and highly sensitive. In addition, the determination of these fifteen elements can be carried out at the same time, which can meet the requests of actual sample analysis. The experimental results showed that some beneficial elements to human such as Ca, Mg, Fe, Zn, Mn, Cu and Na in grapefruit were abundant, while some comparatively harmful elements (Be, Pb, Bi, Cd and As) were not detected. Regional differences and partial differences obviously existed in the concentrations of one or more trace elements in grapefruit. As a whole, the concentrations of most elements in flesh were much lower than in other parts of grapefruit. The concentrations of B, Ba, Ca, Sr and Mn were comparatively higher in the seed capsule than in other parts. Cu, Zn and Mg had the highest concentrations in seed compared to other parts. There was little difference between scarfskin and endodermis. And as for the regional differences, the contents of Mn, Zn and Na in Gannan pomelo in all its parts were higher than those in other regions, and the contents of Ba in Guangdong pomelo in all its parts were higher than those in others, while Guangxi pomelo had the highest Fe content. These differences might resulted from the natural environmental conditions such as temperature, humidity, soil types with different pH, the mineral composition or concentration, and so on. Application of fertilizer and prunning might be an important man-made factors which could also result in the differences. The determination of these elements by using ICP-AES has important point for exploiting grapefruit fully in future.

The WRKY transcription factor HpWRKY44 regulates CytP450-like1 expression in red pitaya fruit (Hylocereus polyrhizus).

Red pitaya (Hylocereus polyrhizus) fruit is a high-value, functional food, containing a high level of betalains. Several genes potentially related to betalain biosynthesis, such as cytochrome P450-like (CytP450-like), have been identified in pitaya fruit, while their transcriptional regulation remains unclear. In this work, the potential involvement of a WRKY transcription factor, HpWRKY44, in regulating CytP450-like1 expression in pitaya fruit was examined. HpWRKY44, a member of the Group 1 WRKY family, contains two conserved WRKY motifs and is localized in the nucleus. HpWRKY44 also exhibits trans-activation ability. Gene expression analysis showed that the expression of HpCytP450-like1 and HpWRKY44 increased steadily during pitaya fruit coloration, which corresponded with the production of elevated betalain levels in the fruit. HpWRKY44 was also demonstrated to directly bind to and activate the HpCytP450-like1 promoter via the recognition of the W-box element present in the promoter. Collectively, our findings indicate that HpWRKY44 transcriptionally activates HpCytP450-like1, which perhaps, at least in part, contributes to betalain biosynthesis in pitaya fruit. The information provided in the current study provides novel insights into the regulatory network associated with betalain biosynthesis during pitaya fruit coloration.