AUTHOR=Zhou Yanfei , Karl Tanja , Lewis David H. , McGhie Tony K. , Arathoon Steve , Davies Kevin M. , Ryan Ken G. , Gould Kevin S. , Schwinn Kathy E. TITLE=Production of Betacyanins in Transgenic Nicotiana tabacum Increases Tolerance to Salinity JOURNAL=Frontiers in Plant Science VOLUME=12 YEAR=2021 URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.653147 DOI=10.3389/fpls.2021.653147 ISSN=1664-462X ABSTRACT=

Although red betalain pigments (betacyanins) have been associated with salinity tolerance in some halophytes like Disphyma australe, efforts to determine whether they have a causal role and the underlying mechanisms have been hampered by a lack of a model system. To address this, we engineered betalain-producing Nicotiana tabacum, by the introduction of three betalain biosynthetic genes. The plants were violet-red due to the accumulation of three betacyanins: betanin, isobetanin, and betanidin. Under salt stress, betacyanic seedlings had increased survivability and leaves of mature plants had higher photochemical quantum yields of photosystem II (F_v/F_m) and faster photosynthetic recovery after saturating light treatment. Under salt stress, compared to controls betacyanic leaf disks had no loss of carotenoids, a slower rate of chlorophyll degradation, and higher F_v/F_m values. Furthermore, simulation of betacyanin pigmentation by using a red filter cover improved F_v/F_m value of green tissue under salt stress. Our results confirm a direct causal role of betacyanins in plant salinity tolerance and indicate a key mechanism is photoprotection. A role in delaying leaf senescence was also indicated, and the enhanced antioxidant capability of the betacyanic leaves suggested a potential contribution to scavenging reactive oxygen species. The study can inform the development of novel biotechnological approaches to improving agricultural productivity in saline-affected areas.