Genome-wide identification, characterization and gene expression of BES1 transcription factor family in grapevine (Vitis vinifera L.)

BES1, as the most important transcription factor responsible for brassinolide (BR) signaling, has been confirmed to play a significant role in regulating plant growth and the improvement of stress resistance. The transcriptional regulatory mechanism of BES1 has been well elucidated in several plants, such as Arabidopsis thaliana (A. thaliana), Triticum aestivum L. (T. aestivum), and Oryza sativa L. (O. sativa). Nevertheless, the genome-wide analysis of the BES1 family in Vitis vinifera L. (V. vinifera). has not been comprehensively carried out. Thus, we have conducted a detailed analysis and identification of the BES1 transcription factors family in V. vinifera; a total of eight VvBES1 genes was predicted, and the phylogenetic relationships, gene structures, and Cis-acting element in their promoters were also analyzed. BES1 genes have been divided into three groups (I, II and III) based on phylogenetic relationship analysis, and most of VvBES1 genes were in group III. Also, we found that VvBES1 genes was located at seven of the total nineteen chromosomes, whereas VvBES1-2 (Vitvi04g01234) and VvBES1-5 (Vitvi18g00924) had a collinearity relationship, and their three copies are well preserved. In addition, the intron-exon model of VvBES1 genes were mostly conserved, and there existed several Cis-acting elements related to stress resistance responsive and phytohormones responsive in BES1s genes promoter. Moreover, the BES1 expressions were different in different V. vinifera organs, and BES1 expressions were different in different V. vinifera varieties under saline-alkali stress and heat stress, the expression of VvBES1 also changed with the prolongation of saline-alkali stress treatment time. The above findings could not only lay a primary foundation for the further validation of VvBES1 function, but could also provide a reference for molecular breeding in V. vinifera.

Photocatalytic Reductive Radical-Polar Crossover for a Base-Free Corey-Seebach Reaction

A metal-free generation of carbanion nucleophiles is of prime importance in organic synthesis. Herein we report a photocatalytic approach to the Corey-Seebach reaction. The presented method operates under mild redox-neutral and base-free conditions giving the desired product with high functional group tolerance. The reaction is enabled by the combination of photo- and hydrogen atom transfer (HAT) catalysis. This catalytic merger allows a C-H to carbanion activation by the abstraction of a hydrogen atom followed by radical reduction. The generated nucleophilic intermediate is then capable of adding to carbonyl electrophiles. The obtained dithiane can be easily converted to the valuable α-hydroxy carbonyl in a subsequent step. The proposed reaction mechanism is supported by emission quenching, radical-radical homocoupling and deuterium labeling studies as well as by calculated redox-potentials and bond strengths.

Pot-Economy Autooxidative Condensation of 2-Aryl-2-lithio-1,3-dithianes

The autoxidative condensation of 2-aryl-2-lithio-1,3-dithianes is here reported. Treatment of 2-aryl-1,3-dithianes with n-BuLi in the absence of any electrophile leads to condensation of three molecules of 1,3-dithianes and formation of highly functionalized α-thioether ketones orthothioesters in 51-89% yields upon air exposure. The method was further expanded to benzaldehyde dithioacetals, affording corresponding orthothioesters and α-thioether ketones in 48-97% yields. The experimental results combined with density functional theory studies support a mechanism triggered by the autoxidation of 2-aryl-2-lithio-1,3-dithianes to yield a highly reactive thioester that undergoes condensation with two other molecules of 2-aryl-2-lithio-1,3-dithiane.

Synthesis of ergostane-type brassinosteroids with modifications in ring A

Herein, we present a new strategy for the preparation of a broad range of brassinosteroid biosynthetic precursors/metabolites differing by the ring A fragment. The protocol is based on the use of readily available phytohormones of this class bearing a 2α,3α-diol moiety (epibrassinolide or epicastasterone) as starting materials. The required functionalities (Δ2-, 2α,3α- and 2β,3β-epoxy-, 2α,3β-, 2β,3α-, and 2β,3β-dihydroxy-, 3-keto-, 3α- and 3β-hydroxy-, 2α-hydroxy-3-keto-) were synthesized from 2α,3α-diols in a few simple steps (Corey-Winter reaction, epoxidation, oxidation, hydride reduction, etc.).

Brassinosteroid-BODIPY conjugates: Design, synthesis, and properties

Three BS-BODIPY (brassinosteroids-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) conjugates were synthesized and their fluorescent and immunological properties were investigated. Two of the conjugates, having present all the functional groups characteristic of BS, were shown to be potentially useful as biological probes to study involvement of BS into physiological processes in living cells.

Synthesis of brassinosteroids with a keto group in the side chain

The aim of this work was to prepare 24-epicryptolide and 22-dehydro-24-epibrassinolide as possible metabolites of 24-epibrassinolide. The main synthetic problem to be solved was the differentiation of functional groups in brassinosteroids. Distinguishing 2α,3α-diol function from another diol group in 24-epibrassinolide was achieved via selective hydrolysis of 2α,3α-cyclic carbonate or via regioselective reaction of boric acid with the functional groups in the side chain. The hydroxyl at C-23 was more reactive than the 22-OH in the oxidation with bromine in the presence of bis(tributyltin) oxide and in the benzylation reaction that resulted in the predominant formation of the corresponding α-hydroxy ketone derivatives with the ratio ranging from 4:1 to 1.5:1.