AFM Investigation of the Organization of Actin Bundles Formed by Actin-Binding Proteins

AFM is a powerful technique for revealing the morphological features of various biological systems at high resolution. However, one of the complications of AFM is that samples must be attached to a flat surface in order to obtain images. This often requires the development of specialized methods depending on the sample which is being used. In this study, we developed a novel technique to image actin bundles on the mica surface. Using this technique, we were able to image molecular assemblies of F-actin with two actin remodeling proteins: α-actinin and Caprice. High resolution AFM images of F-actin fibers and bundle organization depicted two different types of molecular assemblies: F-actin bundles forming an elongated “zipper” structure in the presence of α-actinin, and bundles forming a perpendicularly crossing the mesh structure in the presence of Caprice.

Preparation of DHA-and EPA-enriched Glycerides by Enzymatic Interesterification Using Tuna Oil and Capric Acid

This study focused on the preparation of docosahexaenoic acid(DHA) and eicosapentaenoic acid(EPA)enriched-triacylglycerols by enzymatic interesterification using tuna oil and capric acid. The content of DHA+EPA is 26.86% in the tuna oil used in this study. A response surface methodology(RSM) was used to optimize the reaction parameters(reaction temperature, substrate molar ratio, enzyme amount and reaction time), and the optimized conditions were determined to be: reaction temperature 58℃, substrate molar ratio(capric acid : tuna oil) 4:1, enzyme amount 4%, and reaction time 7.5 h. Under the optimized conditions, the content of DHA+EPA in the glycerides was 40.03%, which is 13.17% higher than that in raw tuna oil. In addition,the MLM-type structured lipids containing medium chain fatty acids(capric acid) at positions sn-1,3 and a long chain fatty acid(DHA/EPA) at the position sn-2 may have many health benefits for humans.

CPC, a Single-Repeat R3 MYB, Is a Negative Regulator of Anthocyanin Biosynthesis in Arabidopsis

Single-repeat R3 MYB transcription factors like CPC （CAPRICE） are known to play roles in developmental processes such as root hair differentiation and trichome initiation. However, none of the six Arabidopsis single-repeat R3 MYB members has been reported to regulate flavonoid biosynthesis. We show here that CPC is a negative regulator of anthocyanin biosynthesis. In the process of using CPC to test GAL4-dependent driver lines, we observed a repression of anthocyanin synthesis upon GAL4-mediated CPC overexpression. We demonstrated that this is not due to an increase in nutrient uptake because of more root hairs. Rather, CPC expression level tightly controls anthocyanin accumulation. Microarray analysis on the whole genome showed that, of 37 000 features tested, 85 genes are repressed greater than three-fold by CPC overexpression. Of these 85, seven are late anthocyanin biosynthesis genes. Also, anthocyanin synthesis genes were shown to be down-regulated in 35S：：CPC overexpression plants. Transient expression results suggest that CPC competes with the R2R3-MYB transcription factor PAP1/2, which is an activator of anthocyanin biosynthesis genes. This report adds anthocyanin biosynthesis to the set of programs that are under CPC control, indicating that this regulator is not only for developmental programs （e.g. root hairs, trichomes）, but can influence anthocyanin pigment synthesis.

Control of Directional Macromolecular Trafficking Across Specific Cellular Boundaries:A Key to Integrative Plant Biology

There is now solid evidence that cell-to-cell trafficking of certain proteins and RNAs plays a critical role in trans-cellular regulation of gene expression to coordinate cellular differentiation and development. Such trafficking also is critical for viral infection and plant defense. The mechanisms of trafficking remain poorly understood. Although some proteins may move between cells by diffusion, many proteins and RNAs move in a highly regulated fashion. Regulation is likely achieved through interactions between distinct protein or RNA motifs and cellular factors. Some motifs and factors have been identified. One of the major focuses for future studies is to identify all motifs and their cognate factors and further elucidate their roles in trafficking between specific cells. With increasing information from such studies, we should be able to develop an understanding of the mechanisms that regulate trafficking of various proteins and RNAs across all and specific cellular boundaries. On the basis of such mechanistic knowledge, we can further investigate how the trafficking machinery has evolved to regulate developmental and physiological processes in a plant, how pathogens have co-evolved to use this machinery for systemic spread in a plant, and how plants use this machinery for counterdefense.