Overexpressing plant ferredoxin-like protein enhances photosynthetic efficiency and carbohydrates accumulation in Phalaenopsis.

Crassulacean acid metabolism (CAM) is one of three major models of carbon dioxide assimilation pathway with better water-use efficiency and slower photosynthetic efficiency in photosynthesis. Previous studies indicated that the gene of sweet pepper plant ferredoxin-like protein (PFLP) shows high homology to the ferredoxin-1(Fd-1) family that belongs to photosynthetic type Fd and involves in photosystem I. It is speculated that overexpressing pflp in the transgenic plant may enhance photosynthetic efficiency through the electron transport chain (ETC). To reveal the function of PFLP in photosynthetic efficiency, pflp transgenic Phalaenopsis, a CAM plant, was generated to analyze photosynthetic markers. Transgenic plants exhibited 1.2-folds of electron transport rate than that of wild type (WT), and higher CO₂ assimilation rates up to 1.6 and 1.5-folds samples at 4 pm and 10 pm respectively. Enzyme activity of phosphoenolpyruvate carboxylase (PEPC) was increased to 5.9-folds in Phase III, and NAD⁺-linked malic enzyme (NAD⁺-ME) activity increased 1.4-folds in Phase IV in transgenic plants. The photosynthesis products were analyzed between transgenic plants and WT. Soluble sugars contents such as glucose, fructose, and sucrose were found to significantly increase to 1.2, 1.8, and 1.3-folds higher in transgenic plants. The starch grains were also accumulated up to 1.4-folds in transgenic plants than that of WT. These results indicated that overexpressing pflp in transgenic plants increases carbohydrates accumulation by enhancing electron transport flow during photosynthesis. This is the first evidence for the PFLP function in CAM plants. Taken altogether, we suggest that pflp is an applicable gene for agriculture application that enhances electron transport chain efficiency during photosynthesis.