Cotton fiber is an excellent model system of cellulose biosynthesis; however, it has not been widely studied due to the lack of information about the cellulose synthase (CESA) family of genes in cotton. In this study, we initially identified six full-length CESA genes designated as GhCESA5-GhCESA10. Phylogenetic analysis and gene co-expression profiling revealed that CESA1, CESA2, CESA7, and CESA8 were the major isoforms for secondary cell wall biosynthesis, whereas CESA3, CESA5, CESA6, CESA9, and CESA10 should involve in primary cell wall formation for cotton fiber initiation and elongation. Using integrative analysis of gene expression patterns, CESA protein levels, and cellulose biosynthesis in vivo, we detected that CESA8 could play an enhancing role for rapid and massive cellulose accumulation in Gossypium hirsutum and Gossypium barbadense. We found that CESA2 displayed a major expression in non-fiber tissues and that CESA1, a housekeeping gene like, was predominantly expressed in all tissues. Further, a dynamic alteration was observed in cell wall composition and a significant discrepancy was observed between the cotton species during fiber elongation, suggesting that pectin accumulation and xyloglucan reduction might contribute to cell wall transition. In addition, we discussed that callose synthesis might be regulated in vivo for massive cellulose production during active secondary cell wall biosynthesis in cotton fibers.
Direct construction of N−C axial chirality via Pd-catalyzed atroposelective C−H olefination of N-arylindoles is reported. The crucial role of chiral amino acid as a cocatalyst in the regio-and stereocontrol has been disclosed. In this reaction, a wide range of arylindoles and functional alkenes could be well tolerated. Moreover, the practicality and synthetic value of this process were demonstrated by the divers and simple transformations of the products.
Histone ubiquitination affects the
structure and function of nucleosomes
through tightly regulated dynamic reversible processes. The efficient
preparation of ubiquitinated histones and their analogs is important
for biochemical and biophysical studies on histone ubiquitination.
Here, we report the CAACU (cysteine-aminoethylation assisted chemical
ubiquitination) strategy for the efficient synthesis of ubiquitinated
histone analogs. The key step in the CAACU strategy is the installation
of an N-alkylated 2-bromoethylamine derivative into a recombinant
histone through cysteine aminoethylation, followed by native chemical
ligation assisted by Seitz’s auxiliary to produce mono- and
diubiquitin (Ub) and small ubiquitin-like modifier (SUMO) modified
histone analogs. This approach enables the rapid production of modified
histones from recombinant proteins at about 1.5–6 mg/L expression.
The thioether-containing isopeptide bonds in the products are chemically
stable and bear only one atomic substitution in the structure, compared
to their native counterparts. The ubiquitinated histone analogs prepared
by CAACU can be readily reconstituted into nucleosomes and selectively
recognized by relevant interacting proteins. The thioether-containing
isopeptide bonds can also be recognized and hydrolyzed by deubiquitinases
(DUBs). Cryo-electron microscopy (cryo-EM) of the nucleosome containing
H2BKC34Ub indicated that the obtained CAACU histones were
of good quality for structural studies. Collectively, this work exemplifies
the utility of the CAACU strategy for the simple and efficient production
of homogeneous ubiquitinated and SUMOylated histones for biochemical
and biophysical studies.
We developed a novel dehydroalanine-based E2-Ub ABP using a strategy that is combination of practical hydrazide-based native chemical ligation and sequential Dha formation.
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