Physiology of rice tungro virus disease: Proline accumulation due to infection

Abstract

Tungro virus infection stimulates proline accumulation in leaves of rice (Oryza sativa L.), especially in a sensitive cultivar, Taichung Native 1. Disease‐induced proline accumulation increases with the severity of the disease. Proline also accumulates in senescing, detached healthy rice leaves. The magnitude of proline accumulation in these leaves was further accentuated by ABA and retarded by kinetin. In the absence of drought stress, virus infection induces severe symptoms (stunting) in a drought tolerant cultivar (Lalnakanda 41) when compared to cultivars with intermediate (MW 10) and high sensitivity (Cauvery) to drought. Thus tungro virus mimics water stress in inducing proline accumulation in rice leaves. In both cases a common factor, ABA, may mediate proline accumulation. In drought stress, proline accumulation is associated with tolerance, while in virus stress, proline accumulation is connected with sensitivity. It is, therefore, clear that proline cannot always act to relieve physiological stress.

Reduction of Light-Induced Anthocyanin Accumulation in Inoculated Sorghum Mesocotyls1

“…Disease-induced re- duction of anthocyanin accumulation in plant tissues has been investigated only to a limited extent. Inoculation with tungro virus reduced the contents of both anthocyanins and flavanols in rice plants, and the reduction was markedly greater in the susceptible cultivar than in either a cultivar with intermediate resistance or a tolerant cultivar (Mohanty and Sridhar, 1989). Similarly, susceptible cultivars of maize inoculated with C. heterostrophus (B. maydis) accumulated significantly lower levels of anthocyanins before lesion development (Heim et al, 1983).…”

Proline Dehydrogenase Contributes to Pathogen Defense in Arabidopsis

“…However, as transgenic flax plants reducing P5CDH expression show normal responses to virulent and avirulent rust infections, the function of fis1 and Pro catabolism in rust disease remains unclear (Mitchell et al, 2006). At the biochemical level, several works have reported the accumulation of Pro in tissues infected with viral (Mohanty and Sridhar, 1982;Radwan et al, 2007) and bacterial (Meon et al, 1978;Fabro et al, 2004) pathogens. In tobacco (Nicotiana tabacum), Pro accumulation is related to susceptibility to Agrobacterium tumefaciens, as Pro antagonizes plant defenses by interfering with the g-aminobutyrate-mediated degradation of bacterial quorum-sensing signals that normally increase pathogen spread (Haudecoeur et al, 2009).…”

Potential of <i>Vigna unguiculata</i> as a Phytoremediation Plant in the Remediation of Zn from Contaminated Soil

“…Several reports show a significant role of proline in osmotic adjustment, protecting cell structure and its function in plants and cultivars of many crops [26] [27]. Proline accumulates in many plant species under a broad range of abiotic stresses as water shortage, salinity, extreme temperatures, and heavy metal accumulation [28]- [31] as well as under biotic stresses [32] [33]. At the structural level, proline protects folded protein structures against denaturation by functioning as a hydroxyl radical scavenger and also stabilizes cell membranes by interacting with phospholipids.…”