Paper Reviewed
Li, X., Zhao, J., Shang, M., Song, H., Zhang, J., Xu, X., Zheng, S., Hou, L., Li, M. and Xing, G. 2020. Physiological and molecular basis of promoting leaf growth in strawberry (Fragaria ananassa Duch.) by CO2 enrichment. Biotechnology & Biotechnological Equipment 34: 905-917.

Strawberry (Fragaria ananassa) is a popular fruit known for its rich nutrition and sweet taste. In a previous study Zhao et al. (2018) reported that elevated CO2 improved strawberry fruit growth, yield and quality. Now, in a follow up paper, Li et al. (2020) explored the physiological and molecular mechanisms driving such changes. In doing so they examined the growth rate and photosynthetic indices in strawberry leaves under ambient and elevated CO2, while also performing transcriptome profiling by RNA sequencing on leaves from the two CO2 treatments in an effort to elucidate gene regulation of photosynthesis in a CO2-enriched environment.

The work was conducted in the Chinese Solar Greenhouse of Shanxi Agricultural University (China). Plants were grown under normal greenhouse production methods at CO2 concentrations of either 400 ppm (ambient) or 800 ppm (elevated), where the elevated CO2 treatment was only enriched during the hours 0730 to 1000 each day. After ten days of CO2 enrichment leaf samples were collected for RNA sequencing.

Results indicated that elevated CO2 significantly enhanced the size, net photosynthetic rate and light saturation point of the leaves, indicating in the authors' words that "photosynthetic rate and related metabolic processes are markedly enhanced by elevated CO2." Transcriptome profiling of leaf tissues revealed 150 differentially expressed genes (DEG) in response to CO2 enrichment, 98 of which were up-regulated and 52 of which were down-regulated. And of the 150 DEGs, 132 exhibited 1.5 to 10-fold changes while 13 exhibited 10 to 50-fold changes.

Further analysis of the DEGs revealed that elevated CO2 (1) "enhanced the biosynthesis of metabolism-promoting growth hormones," (2) accelerated the process of converting active chemical energy into stabilized chemical energy, i.e., it "sped up the reduction step of CO2 assimilation," and (3) "increased the transport of photosynthetic products," all of which changes "help explain the increased net photosynthetic rate and accelerated leaf growth under elevated CO2."

Commenting on these findings, Li et al. write that a "better and deeper understanding of the specific functions of these genes could help us develop molecular tools to drastically increase strawberry yields while maintaining and possibly improving fruit quality, [which] new knowledge could benefit fruit growers and all consumers."

Reference
Zhao, J., Lan, H., Shen, Y.N., et al. 2018. Effects of carbon-rich on quality and growth characteristics of fruit in strawberry. J Shanxi Agric Sci. 46: 538-543.