Enhancement of Photosynthesis and Alleviation of Abiotic Stress in Plants through Bovine Serum Albumin-Capped Gold Nanoclusters

Enhancing light-harvesting and reactive oxygen species scavenging are two promising ways to improve natural photosynthesis efficiency and plant growth. We herein report a bovine serum albumin-capped gold nanocluster with red fluorescent emission and antioxidase-like activity for plant application. This ultrasmall nanocluster could effectively cross the plant root barrier system and transport a long distance to mesophyll cells through the plant vascular systems. On the one hand, the nanocluster expanded the light-harvesting spectrum of A. thaliana seedlings and lettuce, promoting their growth in a typical growth environment. On the other hand, this nanocluster alleviated plant abiotic stress via antioxidase-like activity and maintained the regular operation of the photosynthetic system and the growth of A. thaliana seedlings. The stress indicator FV/FM showed improvements, increasing from 0.63 to 0.71 when exposed to 100 mM NaCl and from 0.58 to 0.74 under 50 μM CdCl2, following treatment with 500 μg mL–1 BSA-AuNCs. RNA-sequencing-based transcriptomic analyses of gene expression change in A. thaliana revealed photosynthesis enhancement and abiotic stress alleviation for BSA-AuNCs. The biosafety consideration was also evaluated with mice fed this nanocluster, and no physiological burden could be detected. Based on the findings above, our biocompatible ultrasmall nanocluster has the potential to be further translated for agricultural applications.