Rice stripe virus (RSV), a typical member of the genus
Tenuvirus, is transmitted mainly by the small brown planthopper (
Laodelphax striatellus) (SBPH) in a persistent and propagative manner, and can infect many crops, such as rice, wheat, and several other gramineous plants, resulting in a severe loss of grain [
1]; in addition, Sun et al. reported that the virus can also infect
Arabidopsis thaliana [
2]. The infected plants exhibit typical symptoms, such as alternating yellow and green stripes, curly and drooping leaves, and necrotic lesions [
3]. Previous reports indicated that the plant chloroplasts were damaged by excessive accumulation of starch, which was triggered by RSV infection, resulting in alternating yellow and green stripes [
4]. Melatonin (N-acetyl-5-methoxytryptamine, MT), an amine hormone that was isolated and identified from the pineal gland in the late 1950s, has been revealed to possess a broad spectrum of biological functions in both animals and plants in many studies [
5‐
9]. In particular, MT has been considered as a therapeutic indole for combating viral diseases, such as SARS (
severe acute respiratory syndrome) and WNV (
West Nile virus) [
10]. Consistent with the benefits of MT in immunology and medicine in animals, MT can also induce plant resistance to pathogens, such as
Pseudomonas syringae DC3000,
Alternaria spp., and
Fusarium spp. [
11,
12]. However, the detailed mechanisms of MT -triggered plant innate immunity to viruses are elusive. Recently, several studies also indicated the potential involvement of a gaseous signal molecule or plant hormone in the defense response triggered by MT. For example, it was reported that nitric oxide (NO) induced by MT is responsible for disease resistance to
Pst DC3000 infection in
Arabidopsis [
13]. Indeed, the vital role of NO in plant-pathogen interactions has been demonstrated by many studies [
14‐
18]. NO can be produced through the nitrate/nitrite-dependent pathway that is known to be catalyzed by nitrate reductase (NR) [
19] and through the
L-arginine-dependent pathway that is known to be catalyzed by a mammalian NO synthase (NOS)-like enzyme [
20,
21]. Further, Lee et al. found that the disease resistance induced by MT correlates with plant hormones in
Pst DC3000 [
11,
22]. Thus, these studies may provide a potential mechanism for the effect of MT and NO in plant against other pathogen infections.
In this study, the endogenous MT level was monitored and quantified in rice after RSV infection. Further, the link among MT, NO and resistance genes was investigated.