The post-illumination chlorophyll fluorescence transient indicates the RuBP regeneration limitation of photosynthesis in low light in Arabidopsis

AbstractThe mechanism of post-illumination chlorophyll fluorescence transient (PIFT) was investigated in Arabidopsis. PIFT was detected in the wild type after illumination with low light. In the fba3-2 (fructose-1,6-bisphosphate aldolase) mutant, in which PIFT is enhanced, strong light also induced PIFT. PIFT was suppressed not only in the triose phosphate/phosphate translocator (tpt-2) mutant, but also in tpt-2 fba3-2, suggesting that triose phosphates, such as dihydroxyacetone phosphate (DHAP), are involved in the PIFT mechanism. We concluded that PIFT is associated with ribulose-1,5-bisphosphate (RuBP)-regeneration limitation of photosynthesis in low light

Gymnosperms have increased capacity for electron leakage to oxygen (Mehler and PTOX reactions) in photosynthesis compared with angiosperms

Oxygen plays an important role in photosynthesis by participating in a number of O2-consuming reactions. O2 inhibits CO 2 fixation by stimulating photorespiration, thus reducing plant production. O2 interacts with photosynthetic electron transport in th

Variations in the Expression of Photosynthesis–Related Proteins in Field Chattonella Marina Cells During a Harmful Algal Bloom

Time series variations in protein expression profiles in field Chattonella marina cells were investigated during a HAB occurred in the inner part of Ariake Sea, Japan (5–14 September, 2012). This study aimed to gather information on the molecular mechanisms underlying the physiological responses in field C. marina population during HAB. Proteomic analysis showed that the abundance of ~37% protein spots (40 out of 108 detected from 2–DE gel images) significantly varied with the sampling date. Significant decreases in the abundances of proteins involved in photosystem II (LHCP 4), electron transfer chain (Cyt c553), Calvin cycle (GAPDH), and chloroplast antioxidant system (2–Cys Prx) were observed as the bloom progressed, suggesting the efficiencies of those photosynthetic pathways declined during the bloom. In addition, the abundances of the above proteins showed significant positive correlations with the F_v/F_m ratio and growth rate of C. marina and with DIN concentrations (except LHCP 4). Our findings suggested that declined expressions of those photosynthesis–related proteins presented some molecular foundation of the decreases in F_v/F_m ratio and growth rate of C. marina during the bloom, and also provided insight into mechanistic links between the external/internal factors and physiological responses of C. marina that may ultimately dictate the ecology of the bloom

Modulating the activities of chloroplasts and mitochondria promotes adenosine triphosphate production and plant growth

Efficient photosynthesis requires a balance of ATP and NADPH production/consumption in chloroplasts, and the exportation of reducing equivalents from chloroplasts is important for balancing stromal ATP/NADPH ratio. Here, we showed that the overexpression of purple acid phosphatase 2 on the outer membranes of chloroplasts and mitochondria can streamline the production and consumption of reducing equivalents in these two organelles, respectively. A higher capacity of consumption of reducing equivalents in mitochondria can indirectly help chloroplasts to balance the ATP/NADPH ratio in stroma and recycle NADP+, the electron acceptors of the linear electron flow (LEF). A higher rate of ATP and NADPH production from the LEF, a higher capacity of carbon fixation by the Calvin-Benson-Bassham (CBB) cycle and a greater consumption of NADH in mitochondria enhance photosynthesis in the chloroplasts, ATP production in the mitochondria and sucrose synthesis in the cytosol and eventually boost plant growth and seed yields in the overexpression lines