Playing a key role in plant growth and development, leaves need to be continuously supplied with water and carbon dioxide to fulfil their photosynthetic function. On its way through the leaf from the xylem to the stomata, water can either move through cell walls or pass from cell to cell to cross the different tissues. Although both pathways are probably used to some degree, evidence is accumulating that living cells contribute substantially to the overall leaf hydraulic conductance (K(leaf)). Transcellular water flow is facilitated and regulated by water channels in the membranes, named aquaporins (AQPs). This review addresses how AQP expression and activity effectively regulate the leaf water balance in normal conditions and modify the cell membrane water permeability in response to different environmental factors, such as irradiance, temperature, and water supply. The role of AQPs in leaf growth and movement, and in CO(2) transport is also discussed.

Leaves are key organs for evaporation and photosynthesis and play a crucial role in plant growth and development. In order to function properly, they need to maintain a balanced water content. Water movement through a leaf occurs by a combination of different pathways: water can follow an apoplastic route through the cell wall or a cell-to-cell route via the symplastic and transcellular paths. As aquaporins (AQPs) play an important role in regulating transcellular water flow and CO(2) conductance, studies on AQP mRNA and protein expression in leaves are essential to better understand their role in these physiological processes. Here, we quantified and localized the expression of Zea mays plasma membrane aquaporins (ZmPIPs, plasma membrane intrinsic proteins) in the leaf using quantitative RT-PCR and immunodetection. All ZmPIP genes except ZmPIP2;7 were expressed in leaves. Expression was found to be dependent on the developmental stage of the leaf tissue, with, in general, an increase in expression at the end of the elongation zone and a decrease in mature leaf tissue. These data correlated with the cell water permeability, as determined using a protoplast swelling assay. The diurnal expression of ZmPIPs was also investigated and expression was found to be higher during the first hours of the light period than at night. Immunocytochemical localization of four ZmPIP isoforms indicated that they are involved in leaf radial water movement, in particular in vascular bundles and the mesophyll.

Global efforts to monitor and contain the Covid-19 pandemic, caused by the beta-coronavirus SARS-CoV-2, currently rely on RT-qPCR-based diagnostic assays. Yet their high cost, moderate throughput, and dependence on sophisticated equipment limit a broad implementation. Loop-mediated isothermal amplification (RT-LAMP) is an alternative detection method that has the potential to overcome these limitations. Here, we established a robust, highly sensitive and versatile RT-LAMP-based SARS-CoV-2 detection assay that is insensitive to carry-over contaminations. Our approach uses a rapid upfront lysis step and hydroxy-naphthol-blue (HNB) for colorimetric detection, which enables the robust identification of Covid-19 infections from a variety of sample types within 30 minutes. By combining RT-LAMP with a simple nucleic acid enrichment method (bead-LAMP), we profoundly increased assay sensitivity to RT-qPCR-like levels, thereby extending applications to large-scale pooled testing. Finally, we developed HomeDip-LAMP for pipette-free SARS-CoV-2 detection for low-resource environments. Our combined optimizations set the stage for implementing RT-LAMP as SARS-CoV-2 diagnostics assay for population-wide and home-based testing.