Response of plasmodesmata formation in leaves of C₄ grasses to growth irradiance

Abstract

Rapid metabolite diffusion across the mesophyll (M) and bundle sheath (BS) cell interface in C 4 leaves is a key requirement for C 4 photosynthesis and occurs via plasmodesmata (PD). Here, we investigated how growth irradiance affects PD density between M and BS cells and between M cells in two C 4 species using our PD quantification method, which combines three-dimensional laser confocal fluorescence microscopy and scanning electron microscopy. The response of leaf anatomy and physiology of NADP-ME species, Setaria viridis and Zea mays to growth under different irradiances, low light (100 μmol m −2 s −1 ), and high light (1,000 μmol m −2 s −1 ), was observed both at seedling and established growth stages. We found that the effect of growth irradiance on C 4 leaf PD density depended on plant age and species.The high light treatment resulted in two to four-fold greater PD density per unit leaf area than at low light, due to greater area of PD clusters and greater PD size in high light plants. These results along with our finding that the effect of light on M-BS PD density was not tightly linked to photosynthetic capacity suggest a complex mechanism underlying the dynamic response of C 4 leaf PD formation to growth irradiance.

High light and temperature reduce photosynthetic efficiency through different mechanisms in the C4 model Setaria viridis

“…Red-blue actinic light (90%/10%) and 3–6 biological replicates for each treatment were used for all measurements. We used a leaf temperature of 25 °C for light and CO 2 response curves as described in previous publications for S. viridis regardless of growth temperatures 56 , 98 , 109 – 111 . During all measurements, the instrument parameters were consistent and stable.…”

On the road to C4 rice: advances and perspectives

“…Therefore, the observation that BS chloroplasts of NADP‐ME plants are mostly agranal with little or no grana thylakoids functionally reflects the reduced PSII, which would normally be located in the granal stacks (see Munekage and Taniguchi, ). However, grana content in BS chloroplasts of NADP‐ME plants is rather variable between species (Ueno et al , ) and also within species in response to environmental conditions (Omoto et al , ; Danila et al , ) and depending on leaf age (Andersen et al , ). It has also been shown that aspartate can be used as a transported C 4 acid in many NADP‐ME type C 4 plants, providing some flexibility in the amount of reducing power transferred to the BS from the M and suggesting that PSII content in the BS cells might in fact respond to the NADPH/NADP + ratio or the redox state of the BS cells (see Furbank, ).…”

Up-regulation of bundle sheath electron transport capacity under limiting light in C4Setaria viridis

“…(2019). Ultrathin sections for transmission electron microscopy (TEM) were prepared after Danila et al . (2019) and examined using a Hitachi HA7100 (Hitachi High Technologies, Santa Clara, CA) at 75 kV.…”

“…Therefore, long- and short-term acclimations to low light are highly relevant for crop productivity (Bellasio and Griffiths, 2014, Sage, 2014). Reports of PSII activity and grana development in BS cells of NADP-ME plants show great variability depending on the growth conditions and suggest a contribution of electron transport machinery to light acclimation (Andersen et al ., 1972, Drozak and Romanowska, 2006, Hasan et al ., 2006, Danila et al ., 2019). Despite the growing interest in improving C 4 photosynthesis and attempts to introduce it into C 3 crop plants (von Caemmerer and Furbank, 2016, Ermakova et al ., 2019, Ermakova et al ., 2020b), little is known of environmental responses and regulatory mechanisms of electron transport at the cell-specific level.…”