Comparative transcriptome analysis reveals photosynthesis divergence in Nicotiana tabacum

Green plants capture sunlight through photosynthetic pigments, converting light energy into chemical energy and fix atmospheric CO 2 into organic molecules essential for life. Crop biomass is determined by carbon assimilation during the growing season. Photosynthesis consists of light reactions and the Calvin-Benson cycle. Thus crop biomass is determined by two pivotal factors: the capacity to capture light energy (e.g., via photosynthetic pigments) and the efficiency of converting light energy into chemical energy stored in organic compounds through carbon assimilation pathways. ZY157 is an elite flue-cured tobacco strain cultivated through successive generations of selection from space-mutated K326 lines, and Y87 is the hybrid progeny of K326. Both of them exhibit higher biomass, more vigorous growth and stronger disease resistance compared to K326. Physiological analyses of ZY157, K326, and Y87 showed that chlorophyll a, chlorophyll b, lutein and β-carotene content was significantly higher in ZY157 and Y87 than in K326. Transcriptomic analyses further revealed upregulated expression of key genes involved in chlorophyll and carotenoid biosynthesis in ZY157 and Y87 compared to K326. Moreover, some important genes of light reactions and the Calvin cycle were upregulated in ZY157 and Y87 compared to K326, including FNR , ATPD , SBPase and so on. The net photosynthetic rates of ZY157 and Y87 were significantly higher than that of K326. These results indicated that the photosynthesis divergence among ZY157, Y87 and K326 probably contributed to the growth differences among them. Our findings will provide theoretic basis and breeding materials for high photosynthetic efficiency breeding. • ZY157, space-mutated K326, shows significantly higher biomass and enhanced disease resistance potential. • Upregulation of photosynthesis-related genes accompanies the higher net photosynthetic rates observed in ZY157 and Y87. • The improved photosynthetic efficiency in ZY157 and Y87 may be a key mechanism underlying their growth advantages. • Transcriptome analysis is an effective method for studying the genetic basis of photosynthesis divergence in tobacco.