Comparative study of two indoor microbial volatile pollutants, 2-Methyl-1-butanol and 3-Methyl-1-butanol, on growth and antioxidant system of rice (Oryza sativa) seedlings.

2-Methyl-1-butanol (2MB) and 3-Methyl-1-butanol (3MB) are microbial volatile organic compounds (VOCs) and found in indoor air. Here, we applied rice as a bioindicator to investigate the effects of these indoor microbial volatile pollutants. A remarkable decrease in germination percentage, shoot and root elongation, as well as lateral root numbers were observed in 3MB. Furthermore, ROS production increased by 2MB and 3MB, suggesting that pentanol isomers could induce cytotoxicity in rice seedlings. The enhancement of peroxidase (POD) and catalase (CAT) activity provided evidence that pentanol isomers activated the enzymatic antioxidant scavenging systems, with a more significant effect observed in 3MB. Furthermore, 3MB induced higher activity levels of glutathione (GSH), oxidized glutathione (GSSG), and the GSH/GSSG ratio in rice compared to the levels induced by 2MB. Additionally, qRT-PCR analysis showed more up-regulation in the expression of glutaredoxins (GRXs), peroxiredoxins (PRXs), thioredoxins (TRXs), and glutathione S-transferases (GSTUs) genes in 3MB. Taking the impacts of pentanol isomers together, the present study suggests that 3MB exhibits more cytotoxic than 2MB, as such has critical effects on germination and the early seedling stage of rice. Our results provide molecular insights into how isomeric indoor microbial volatile pollutants affect plant growth through airborne signals.

Volatile cinnamaldehyde induces systemic salt tolerance in the roots of rice (Oryza sativa).

Cinnamaldehyde (CA) is a volatile plant secondary metabolite that exhibits strong anti-pathogenic activities. Nonetheless, less is known about the effect of CA on plant tolerance to abiotic stresses. In this study, we delineated the effects of CA fumigation on rice roots (Oryza Sativa L cv. TNG67) under salinity stress (200 mM NaCl). Our result showed that CA vapor significantly alleviated salinity-induced ROS accumulation and cell death. This CA-induced alleviation appears to be mediated primarily by the upregulation of proline metabolism genes, the rapid proline accumulation, and the decrease of Na+ /K+ ratio as early as 3 h after NaCl treatment. Of note, the activities of peroxidase (POD; EC 1.11.1.7) isozymes a and b were decreased by CA fumigation, and the activities of catalase (CAT; EC 1.11.1.6) and superoxide dismutase (SOD; EC 1.15.1.1) were not significantly affected. Our findings suggest that CA vapor might be useful for priming rice roots to withstand salinity stress, which is more prevalent due to the ongoing global climate change. To the best of our knowledge, this is the first study to show modulation of macro- and micro-elements as well as antioxidative factors after CA fumigation of salinity-stressed rice roots.