A conserved but plant-specific CDK-mediated regulation of DNA replication protein A2 in the precise control of stomatal terminal division

The R2R3-MYB transcription factor FOUR LIPS (FLP) controls the stomatal terminal division through transcriptional repression of the cell cycle genes CYCLIN-DEPENDENT KINASE (CDK) B1s (CDKB1s), CDKA; 1, and CYCLIN A2s (CYCA2s). We mutagenized the weak mutant allele flp-1 seeds with ethylmethane sulfonate and screened out a flp-1 suppressor 1 (fsp1) that suppressed the flp-1 stomatal cluster phenotype. FSP1 encodes RPA2a subunit of Replication Protein A (RPA) complexes that play important roles in DNA replication, recombination, and repair. Here, we show that FSP1/RPA2a functions together with CDKB1s and CYCA2s in restricting stomatal precursor proliferation, ensuring the stomatal terminal division and maintaining a normal guard-cell size and DNA content. Furthermore, we provide direct evidence for the existence of an evolutionarily conserved, but plant-specific, CDK-mediated RPA regulatory pathway. Serine-11 and Serine-21 at the N terminus of RPA2a are CDK phosphorylation target residues. The expression of the phosphorylation-mimic variant RPA2a(S11,21/D) partially complemented the defective cell division and DNA damage hypersensitivity in cdkb1;1 1;2 mutants. Thus, our study provides a mechanistic understanding of the CDK-mediated phosphorylation of RPA in the precise control of cell cycle and DNA repair in plants

Improved tolerance to drought stress after anthesis due to priming before anthesis in wheat (Triticum aestivum L.) var. Vinjett.

Drought stress occurring during the reproductive growth stage leads to considerable reductions in crop production and has become an important limiting factor for food security globally. In order to explore the possible role of drought priming (pre-exposure of the plants to mild drought stress) on the alleviation of a severe drought stress event later in development, wheat plants were subjected to single or double mild drought episodes (soil relative water content around 35–40%) before anthesis and/or to a severe drought stress event (soil relative water content around 20–25%) 15 d after anthesis. Here, single or double drought priming before anthesis resulted in higher grain yield than in non-primed plants under drought stress during grain filling. The photosynthesis rate and ascorbate peroxidase activity were higher while malondialdehyde content was lower in primed plants than in the non-primed plants under drought stress during grain filling. Proteins in flag leaves differently expressed by the priming and drought stress were mainly related to photosynthesis, stress defence, metabolism, molecular chaperone, and cell structure. Furthermore, the protein abundance of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) small subunit, Rubisco activase and ascorbate peroxidase were upregulated in primed plants compared with non-primed plants under drought stress during grain filling. In conclusion, the altered protein expression and upregulated activities of photosynthesis and ascorbate peroxidase in primed plants may indicate their potential roles in alleviating a later-occurring drought stress episode, thereby contributing to higher wheat grain yield under drought stress during grain filling

The Application of Resonance Light Scattering Technique for the Determination of Tinidazole in Drugs

A resonance light scattering technique to determine tinidazole in drugs was developed by tetraphenylboron sodium (TPB). Tinidazole was found to bind B(C6H5)−4 anion and transformed to tinidazole-TPB aggregate which displayed intense resonance scattering light. Effects of factors such as wavelength, acidity, stabilizers, and interferents on the RLS of tinidazole TPB were investigated in detail. The RLS intensity of the tinidazole-TPB suspension was obtained in sulfuric acid solution (pH = 1.44). The resonance scattering light intensity at the maximum RLS peak of 569.5 nm was linear to the concentration of tinidazole in the range of 10.0–30.0 μg mL−1 with a detection limit of 5.0 μg mL−1. Good results were also obtained with the recovery range of 95.13–106.76%. The method was applied to determine tinidazole in injections and tablets, showing high sensitivity and accuracy compared with the high performance liquid chromatography method (HPLC) according to Chinese Pharmacopoeia