Leaf Eh and pH: A Novel Indicator of Plant Stress. Spatial, Temporal and Genotypic Variability in Rice (Oryza sativa L.)

A wealth of knowledge has been published in the last decade on redox regulations in plants. However, these works remained largely at cellular and organelle levels. Simple indicators of oxidative stress at the plant level are still missing. We developed a method for direct measurement of leaf Eh and pH, which revealed spatial, temporal, and genotypic variations in rice. Eh (redox potential) and Eh@pH7 (redox potential corrected to pH 7) of the last fully expanded leaf decreased after sunrise. Leaf Eh was high in the youngest leaf and in the oldest leaves, and minimum for the last fully expanded leaf. Leaf pH decreased from youngest to oldest leaves. The same gradients in Eh-pH were measured for various varieties, hydric conditions, and cropping seasons. Rice varieties differed in Eh, pH, and/or Eh@pH7. Leaf Eh increases and leaf pH decreases with plant age. These patterns and dynamics in leaf Eh-pH are in accordance with the pattern and dynamics of disease infections. Leaf Eh-pH can bring new insight on redox processes at plant level and is proposed as a novel indicator of plant stress/health. It could be used by agronomists, breeders, and pathologists to accelerate the development of crop cultivation methods leading to agroecological crop protection

LocZ is a new cell division protein involved in proper septum placement in Streptococcus pneumoniae

How bacteria control proper septum placement at midcell, to guarantee the generation of identical daughter cells, is still largely unknown. Although different systems involved in the selection of the division site have been described in selected species, these do not appear to be widely conserved. Here, we report that LocZ (Spr0334), a newly identified cell division protein, is involved in proper septum placement in Streptococcus pneumoniae. We show that locZ is not essential but that its deletion results in cell division defects and shape deformation, causing cells to divide asymmetrically and generate unequally sized, occasionally anucleated, daughter cells. LocZ has a unique localization profile. It arrives early at midcell, before FtsZ and FtsA, and leaves the septum early, apparently moving along with the equatorial rings that mark the future division sites. Consistently, cells lacking LocZ also show misplacement of the Z-ring, suggesting that it could act as a positive regulator to determine septum placement. LocZ was identified as a substrate of the Ser/Thr protein kinase StkP, which regulates cell division in S. pneumoniae. Interestingly, homologues of LocZ are found only in streptococci, lactococci, and enterococci, indicating that this close phylogenetically related group of bacteria evolved a specific solution to spatially regulate cell division. IMPORTANCE Bacterial cell division is a highly ordered process regulated in time and space. Recently, we reported that the Ser/ Thr protein kinase StkP regulates cell division in Streptococcus pneumoniae, through phosphorylation of several key proteins. Here, we characterized one of the StkP substrates, Spr0334, which we named LocZ. We show that LocZ is a new cell division protein important for proper septum placement and likely functions as a marker of the cell division site. Consistently, LocZ supports proper Z-ring positioning at midcell. LocZ is conserved only among streptococci, lactococci, and enterococci, which lack homologues of the Min and nucleoid occlusion effectors, indicating that these bacteria adapted a unique mechanism to find their middle, reflecting their specific shape and symmetry

The TRESLIN-MTBP complex couples completion of DNA replication with S/G2 transition

It has been proposed that ATR kinase senses the completion of DNA replication to initiate the S/G2 transition. In contrast to this model, we show here that the TRESLIN-MTBP complex prevents a premature entry into G2 from early S-phase independently of ATR/CHK1 kinases. TRESLIN-MTBP acts transiently at pre-replication complexes (preRCs) to initiate origin firing and is released after the subsequent recruitment of CDC45. This dynamic behavior of TRESLIN-MTBP implements a monitoring system that checks the activation of replication forks and senses the rate of origin firing to prevent the entry into G2. This system detects the decline in the number of origins of replication that naturally occurs in very late S, which is the signature that cells use to determine the completion of DNA replication and permit the S/G2 transition. Our work introduces TRESLIN-MTBP as a key player in cell-cycle control independent of canonical checkpoints

The kinetoplast DNA structure of

The structure of the kinetoplast DNA (kDNA) network of fish trypanosomes is described for the first time. The kDNA was isolated from lysed cells of trypanosomes grown in culture by differential centrifugation combined with chloroform-isoamyl alcohol extraction. Electron microscopy of spread DNA networks revealed the existence of two kinds of mutually interlocked circular molecules. The maxicircle size was 27.5 ± 2.5 kbp (kilobase pairs) and that of the predominant minicircles 1.9 ± 0.1 kbp