Abstract
Sporulation and spore release are essential phases of the life cycle in algae and land plants. Ulva prolifera, which is an ideal organism for studying sporulation and spore release, was used as the experimental material in the present study. The determination of photosynthetic parameters, combined with microscopic observation, treatment with photosynthetic inhibitors, limitation of carbon acquisition, and protein mass spectrometry, was employed in this experiment. Cycle electron transport (CEF) was found enhanced at the onset of sporangia formation. The inhibition effect of dibromothymoquinone (DBMIB) towards sporulation was always strong during the sporulation process whereas the inhibition effect of 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU) was continuously declined accompanied with the progress of sporulation. The changes of photosynthesis resulted from the limitation of CO2 acquisition could stimulate sporulation onset. Quantitative protein analysis showed that enzymes involved in carbon fixation, including RUBISCO and pyruvate orthophosphate dikinase, declined during sporogenesis, while proteins involved in sporulation, including tubulin and centrin, increased. These results suggest that enhanced cyclic electron flow (CEF) and oxidation of the plastoquinone pool are essential for sporangia formation onset, and changes in photosynthetic electron transport chain have significant impacts on sporulation of the green algae.
Highlights
Sporogenesis is a developmental process that produces spores through cell division and differentiation
Under our regular microscopic observation of the excised disks in culture through sporulation and spore with four flagella release, the formation of sporangia did not occur before 48 h (Fig. 1A–D), but sporulation and spore release occurred by 60 h (Fig. 1E,F)
Both DCMU and DBMIB are photosynthetic inhibitors, which can lead to great changes in the photosynthetic electron transport chain, it is interesting that there are evident differences in inhibition effect towards sporulation between DCMU and DBMIB
Summary
Sporogenesis is a developmental process that produces spores through cell division and differentiation. Photosynthesis consists of two portions, the light and dark reactions These two portions can both influence the regulation of physiological processes in land plants and algae. Campbell et al.[5] suggested that in cyanobacteria the redox status of the plastoquinone pool, which is a component of the photosynthetic electron transport chain, can regulate cellular differentiation, including the formation of hormogonia for reproduction[5]. We employed U. prolifera as an experimental material to investigate the changes of photosynthesis, especially concerning photosynthetic electron transport chain, during sporulation and spore release. Sporulation and spore release can be controlled by adjusting photosynthesis These results suggest that photosynthesis plays a central role in the regulation of spore formation and release in photosynthetic organisms including green algae
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