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In order to ascertain the role of plant transglutaminases (TGase) in growth and abiotic stress response, the AtPng1 knock out (KO) line of A. thaliana has been analyzed during plant development and under heat and wound stress. Comparing wild type (WT) and KO lines a 58-kDa band was immunodetected by anti-AtPng1p antibody in the cell wall and chloroplasts only in the WT line. A residual TGase activity, not showing correlation with development nor stress response, was still present in the KO line. The KO line was less developed, with a juvenile phenotype characterized by fewer, smaller and less differentiated cells. Chloroplast TGase activity was insensitive to mutation. Data on stressed plants showed that (i) KO plants under heat stress were more juvenile compared to WT, (ii) different responses between WT and KO lines after wounding took place. TGase activity was not completely absent in the KO line, presenting high activity in the plastidial fraction. In general, the mutation affected A. thaliana growth and development, causing less differentiated cytological and anatomical features., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Tomato (Solanum lycopersicum L.) is one of the most widely cultivated crops in the world. Tomato is a plant model and the relationship between yield and biotic/abiotic stress has attracted increasing scientific interest. Tomato cultivation under sub-optimal conditions usually negatively impacts growth and development; in particular, heat stress affects several cellular and metabolic processes, such as respiration and photosynthesis. In this work, we studied the effects of chronic heat stress on various cytological and biochemical aspects using the Micro-Tom cultivar as a model. Photosynthetic efficiency decreased during heat stress while levels of post-photosynthetic sugars (sucrose, fructose, glucose and glucose 6-phosphate) oscillated during stress. Similarly, photosynthetic pigments (lutein, chlorophyll a, chlorophyll b and β-carotene) showed an oscillating downward trend with partial recovery during the stress-free phase. The energetic capacity of leaves (e.g. ATP and ADP) was altered, as well as the reactive oxygen species (ROS) profile; the latter increased during stress. Important effects were also found on the accumulation of Rubisco isoforms, which decreased in number. Heat stress also resulted in a decreased accumulation of lipids (oleic and linoleic acid). Photosynthetically alterations were accompanied by cytological changes in leaf structure, particularly in the number of lipid bodies and starch granules. Prolonged heat stress progressively compromised the photosynthetic efficiency of tomato leaves. The present study reports multi-approach information on metabolic and photosynthetic injuries and responses of tomato plants to chronic heat stress, highlighting the plant's ability to adapt to stress., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Cyclophilins (CyPs) are ubiquitous proteins involved in a wide variety of processes including protein maturation and trafficking, receptor complex stabilization, apoptosis, receptor signaling, RNA processing, and spliceosome assembly. The ubiquitous presence is justified by their peptidyl-prolyl cis-trans isomerase (PPIase) activity, catalyzing the rotation of X-Pro peptide bonds from a cis to a trans conformation, a critical rate-limiting step in protein folding, as over 90% of proteins contain trans prolyl imide bonds. In Arabidopsis 35 CyPs involved in plant development have been reported, showing different subcellular localizations and tissue- and stage-specific expression. In the present work, we focused on the localization of CyPs in pear (Pyrus communis) pollen, a model system for studies on pollen tube elongation and on pollen-pistil self-incompatibility response. Fluorescent, confocal and immuno-electron microscopy showed that this protein is present in the cytoplasm, organelles and cell wall, as confirmed by protein fractionation. Moreover, an 18-kDa CyP isoform was specifically released extracellularly when pear pollen was incubated with the Ca 2+ chelator EGTA., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)