Identification of candidate genes associated with photosynthesis in eggplant under elevated CO₂

Elevated CO₂ can stimulate plant growth in greenhouses, but the molecular mechanism behind this response is unclear, especially in eggplants. In this study, we evaluated the physiological and photosynthetic response of the eggplant variety ‘Shenyuan 3’ under elevated CO₂, and the candidate genes related to this response were identified by transcriptomic analysis. The results showed that elevated CO₂ can promote eggplant growth and development in greenhouses; plant height and stem diameter were maximally increased by 28.62% and 5.20%, respectively. Net photosynthetic rate, light saturation point and intercellular CO₂ concentration of eggplant leaves increased by 86.11%, 49.94% and 102.06%, respectively, whereas light compensation point, dark breathing rate and stomatal conductance decreased by 35.90%, 27.30% and 26.03%, respectively. A total of 169 differentially expressed genes (DEGs) were screened, of which 99 were up-regulated and 70 were down-regulated. Gene Ontology (GO) function enrichment analysis suggested that these proteins can be classified into 11 molecular functions, including transcription factors, phosphoenolpyruvate carboxylase and oxidoreductase. Pathway analysis indicated that elevated CO₂ affects plant growth and development by affecting carbon metabolism, carbon fixation, chlorophyll and porphyrin metabolism. Twelve genes were further detected by qRT-PCR, and 11 genes showed similar dynamics with the transcriptomic data. Bilirubin dehydrogenase <i>Sme2.5_04464.1_g00001</i> and the malate dehydrogenase gene <i>Sme2.5_03383.1_g00002</i>, which are involved in the chlorophyll porphyrin pathway and carbon metabolism, respectively, were up-regulated. Transcription factors <i>bHLH</i> (<i>Sme2.5_01232.1_g00025</i>) and GATA (<i>Sme2.5_00372.1_g00006</i>) were also up-regulated under elevated CO₂ treatment. Further research should focus on cloning these genes and identifying their response mechanism under elevated CO₂.

高浓度二氧化碳可促进温室中植物的生长，但该响应背后的分子机制仍不明确，在茄子中尤为如此。本研究以茄子品种‘沈园3号’为材料，评估了其在高浓度二氧化碳处理下的生理与光合响应，并通过转录组分析（transcriptomic analysis）筛选得到与该响应相关的候选基因。结果表明，高浓度二氧化碳可促进温室茄子的生长发育，其株高与茎粗的最大增幅分别可达28.62%与5.20%。茄子叶片的净光合速率、光饱和点及胞间二氧化碳浓度分别提升了86.11%、49.94%与102.06%，而光补偿点、暗呼吸速率与气孔导度则分别下降了35.90%、27.30%与26.03%。本研究共筛选出169个差异表达基因（differentially expressed genes, DEGs），其中99个上调表达，70个下调表达。基因本体（Gene Ontology, GO）功能富集分析显示，这些差异蛋白可分为11类分子功能，涵盖转录因子、磷酸烯醇式丙酮酸羧化酶与氧化还原酶等。通路分析表明，高浓度二氧化碳可通过调控碳代谢、碳固定、叶绿素及卟啉代谢途径影响植物的生长发育。本研究通过实时荧光定量聚合酶链反应（qRT-PCR）对12个候选基因进行了验证，其中11个基因的表达趋势与转录组测序结果一致。参与叶绿素卟啉代谢通路的胆红素脱氢酶基因<i>Sme2.5_04464.1_g00001</i>，以及参与碳代谢的苹果酸脱氢酶基因<i>Sme2.5_03383.1_g00002</i>均呈上调表达。碱性螺旋-环-螺旋（bHLH）转录因子<i>Sme2.5_01232.1_g00025</i>与GATA转录因子<i>Sme2.5_00372.1_g00006</i>在高浓度二氧化碳处理下同样呈现上调表达。未来研究可聚焦于克隆这些基因，并阐明其在高浓度二氧化碳处理下的响应机制。