Chromatin Immunoprecipitation (ChiP) Protocol for the Analysis of Gene Regulation by Histone Modifications in Agave angustifolia Haw

Chromatin is a dynamic entity that regulates different biological processes crucial for the proper functioning of the cell. Chromatin regulation depends largely on the interactions that occur between DNA with histones and nonhistone proteins. The chromatin immunoprecipitation assay (ChiP) is a widely used technique for the study of these DNA-histone and DNA-nonhistone interactions and their biological repercussions. Here we describe a ChiP protocol that allows in vivo analysis of the associations of histone modifications with genomic DNA in Agave angustifolia Haw. Although this protocol is established for A. angustifolia, it can be used in other species to obtain similar results. We also propose a strategy to shorten the times in some steps of the standard protocol.

Carotenoids, versatile components of oxygenic photosynthesis

Carotenoids (CARs) are a group of pigments that perform several important physiological functions in all kingdoms of living organisms. CARs serve as protective agents, which are essential structural components of photosynthetic complexes and membranes, and they play an important role in the light harvesting mechanism of photosynthesizing plants and cyanobacteria. The protection against reactive oxygen species, realized by quenching of singlet oxygen and the excited states of photosensitizing molecules, as well as by the scavenging of free radicals, is one of the main biological functions of CARs. X-ray crystallographic localization of CARs revealed that they are present at functionally and structurally important sites of both the PSI and PSII reaction centers. Characterization of a CAR-less cyanobacterial mutant revealed that while the absence of CARs prevents the formation of PSII complexes, it does not abolish the assembly and function of PSI. CAR molecules assist in the formation of protein subunits of the photosynthetic complexes by gluing together their protein components. In addition to their aforementioned indispensable functions, CARs have a substantial role in the formation and maintenance of proper cellular architecture, and potentially also in the protection of the translational machinery under stress conditions.