Biochemical properties and ultrastructure of mesophyll and bundle sheath thylakoids from maize (Zea mays) chloroplasts

Abstract

A characteristic feature of C4 plants is the differentiation of the photosynthetic leaf tissues into two distinct cell types: mesophyll (M) and bundle sheath (BS) cells. We have investigated several biochemical parameters, including pigment composition, polypeptide patterns, fluorescence at 77K, the activity of photosystems and ultrastructure of mesophyll and bundle sheath chloroplasts of maize (Zea mays L.) plants. It is shown that the BS chloroplasts have ~2-fold higher chlorophyll a/b ratio than M chloroplasts, 6.15 and 3.12 respectively. The PSI apoprotein (68 kDa) was more abundant in BS than in M thylakoids. Polypeptides belonging to PSII core antenna, are in similar amounts in both types of membranes, but the 45kDa band is more intensive in M thylakoids. Polypeptides in the region of 28–24 kDa of the light-harvesting complex of PSII (LHCII) are also present in both types of chloroplasts, though their amounts are reduced in BS thylakoids. The chlorophyll fluorescence emission spectra in M cells showed the presence of three bands at 686, 695 and 735 nm characteristics of LHCII, PSII core and PSI complexes, respectively. However, in the fluorescence spectrum of agranal plastids, there are almost traces of the band at 695 nm, which belongs to the PSII core complex. The research results revealed that the photochemical activity of PSII in BS chloroplasts is ~5 times less than in the chloroplasts of M cells. The highest PSI activity was found in maize BS chloroplasts.

Crop photosynthesis for the twenty-first century

“…Photosynthesis is influenced by multiple environmental factors, including high temperature, drought, salinity, high and fluctuating light, mineral nutrition, and CO 2 concentration (Brestic et al 2018;Ferroni et al 2020;Ibrahimova et al 2021;Li et al 2021). The question of how plants grow under changes in these environmental conditions and how photosynthesis optimization occurs are some of the most important and interesting questions in studying plant growth, for if we are able to quantify the optimal environmental conditions that maximize photosynthesis, they can be employed in controlled environments to increase crop productivity (Aliyeva et al 2020;Hussain et al 2021;Mishra et al 2021;Yan et al 2021). We want to improve the structural and functional properties of the photosynthetic apparatus so that modern varieties are more efficient and effective in the use of water and mineral nutrition resources and more tolerant to environmental changes.…”

Optimising photosynthesis for environmental fitness

“…An increase in the content of H 2 O 2 and malondialdehyde (MDA), as well as alterations in the activities of AsA-GSH cycle enzymes and quantitative changes in AsA and GSH content during the day was observed in leaves of durum (Triticum durum Desf.) and bread (Triticum aestivum L.) wheat genotypes exposed to drought (Aliyeva et al 2020a). Although PSII efficiency was significantly lower in the control and drought exposed leaves at the highest temperature in the afternoon, and the authors observed the increase in activity of ascorbate peroxidase, glutathione reductase and glutathione content at the expense of regeneration of oxidised glutathione.…”