Utilizing Wheat Hybrid Lines to Mine Genes Regulating Cyclic Electron Flow and Applying Them in Improving Photosynthetic Efficiency in Crops

doi:10.13560/j.cnki.biotech.bull.1985.2025-0620

Abstract

Abstract:

Objective Global warming and a rapidly increasing global population present formidable challenges to food security, necessitating significant advancements in both crop yield improvement and enhanced resilience to environmental stresses. Photosynthesis serves as the foundation of crop productivity, with the cyclic electron flow during the light reactions coupling ATP synthesis and modulating reducing power accumulation. This pathway plays an important role in heat adaptation and photosynthetic efficiency, making the identification and application of its genetic regulators imperative. Method This study utilized representative wheat lines with varying cyclic photosynthetic electron transport activities as references, combined with photosynthetic parameter measurements, protein content assays, and transcriptome sequencing techniques. From the recombinant inbred lines derived from the crossbreeding of wheat varieties Xiaoyan 54 and Jing 411, strains exhibiting polar separation in cyclic electron transport activity were screened and differentially expressed genes were obtained. Result The strains with higher cyclic electron transport activity also demonstrated elevated linear electron transport activity and photosynthetic CO₂ assimilation rates, maintaining these advantages under increased light intensity, making them suitable for application as high-efficiency breeding materials. Through differential gene expression analysis, a series of functional genes and transcription factors with potential to enhance cyclic photosynthetic electron transport or overall photosynthetic activity were identified. Selected genes (including TaPnsL2 and TaNAC) were constructed into overexpressing vectors and transformed into the rice cultivar Xiushui 134. The T₁ and T₂ generation transgenic materials presented advantages in photosynthetic rate during field trials in both Hainan province and Shanghai. Conclusion Through genetic screening or modification targeting the activity of cyclic electron transport, there is potential to enhance the photosynthetic efficiency or adaptability to high light intensity in crops.

Key words: cyclic electron transport, photosynthesis, NDH complex, genetic regulation, wheat, rice

FAN Yan-fei, YE Lu-huan, LI Yu-tong, WANG Chuan-luo, ZHANG Rui, LUO Jian-hua, WANG Peng. Utilizing Wheat Hybrid Lines to Mine Genes Regulating Cyclic Electron Flow and Applying Them in Improving Photosynthetic Efficiency in Crops[J]. Biotechnology Bulletin, 2025, 41(10): 72-86.

Figures/Tables 8

Fig. 1 Planting of wheat recombinant inbred population, and measurements of initial P700+ dark-reduction rates and ETR(Ⅰ)- ETR(Ⅱ) in representative varietiesA: The above is a photo of one batch of wheat materials during the first round of P700+ reduction rate measurement; the bottom left shows five representative wheat varieties; the bottom right displays the wheat population growing in the field. B: Left, P700+reduction curves of five representative wheat varieties; right, initial slope of curve decline (bar chart). C: Line chart of ETR(Ⅰ)-ETR(Ⅱ) for five representative wheat varieties under increasing light intensity gradients

Fig. 2 Distribution examples of initial P700+ dark-reduction rates of wheat population in the first-round measurementThe first-round screening of initial P700+ dark-reduction rates covered the entire wheat recombinant inbred line population. Here, the measurements of the first 80 lines (RL01-RL80, “RL” is short for “recombinant inbred line”) are displayed, with every consecutive 20 lines plus 5 representative cultivars measured and plotted as a group. The representative varieties are displayed in blue, while the lines with high and low cyclic electron transport activity selected from both ends of the data distribution are shown in green and light brown, respectively

Fig. 3 Distribution of initial P700+ dark reduction rates of wheat population in the second-round measurementThe second-round initial P700+ dark-reduction rate screening focused on lines with either high or low cyclic electron transport activity from the. They were randomly grouped into 4 batches alongside representative cultivars and measured and graphed usingthe same protocol as the first-round screening. Representative varieties are still shown in blue, while the lines with high and low cyclic electron transport activity selected from the first-round screening remain displayed in green and light brown, respectively. “RL” is short for “recombinant inbred line”

Fig. 4 Growth phenotypes of representative wheat cultivars and light-intensity-dependent photosynthetic parametersA: Five representative wheat varieties after heading. B-D: Net photosynthetic rate (Anet), Y(Ⅱ) and ETR(Ⅱ) of representative varieties under light-intensity gradients. Field measurements of photosynthetic rates and electron transport activities under varying light intensities were conducted on flag leaves of wheat representative cultivars (LX99,SSDL10,XY101, XY54, and J411) using Li-6400 photosynthesis system and PAM-2000 portable chlorophyll fluorometer. The measurements were performed on clear mornings during the post-heading stage, with 4-6 biological replicates per cultivar

Fig. 5 Growth phenotypes of wheat recombinant inbred lines and light-intensity-dependent photosynthetic parametersA: Four wheat recombinant inbred lines after heading. B-D: Net photosynthetic rate (Anet), Y(Ⅱ) and ETR(Ⅱ) of wheat recombinant inbred lines under light-intensity gradients, respectively. Field measurements of photosynthetic rates and electron transport activities under varying light intensities were conducted on flag leaves of wheat recombinant inbred lines (RL18, RL48, RL42 and RL71) using Li-6400 photosynthesis system and PAM-2000 portable chlorophyll fluorometer. The measurements were performed on clear mornings during the post-heading stage, with 5-6 biological replicates per cultivar

Fig. 6 Determination of NDH subunit content in recombinant inbred line populationA: Determination of NDH-H subunit content in recombinant inbred line population (first round). B: Second-round quantification of NDH complex content in the recombinant inbred line population. The Western blot results are comparable within each blot, but the signal intensities may vary between different blots. Each immunoblotting image contains XY101 (high NDH-H content) and LX99 (low NDH-H content) as references

Fig. 7 Analysis example of transcriptome sequencing resultsA-D: Differential expressions of genes related to intersystem electron carriers, cyclic photosynthetic electron transport, PSI and transcription factors respectively. The heatmap demonstrates the logarithmic values |Log2（FC）| of the fold change of FPKM values for each variety relative to the average of “LX99+J411”

Fig. 8 Photosynthetic rate analysis of T1 and T2 generation rice lines overexpressing wheat PnsL2 and NAC genesA-C: Net photosynthetic rate (Anet) of wheat PnsL2 gene-overexpressing rice lines under different measuring light intensities in Hainan and Shanghai. D-F: Net photosynthetic rate (Anet) of wheat transcription factor gene NAC-overexpressing rice lines under different measuring light intensities in Hainan and Shanghai

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