Overexpression of OsTlp Improves Resistance of MR 219 Rice (Oryza sativa spp. Indica) to Sheath Blight

Abstract

Sheath blight, caused by Rhizoctania solani, is one of the major diseases affecting global rice production.
The lack of resistant rice accessions emphasises the necessity for modern biotechnology approaches to
provide an alternative strategy towards selective breeding. Previously, the differential expression of several
pathogenesis-related (PR) protein genes revealed the thaumatin-like protein (OsTlp) gene, part of the
pathogenesis-related PR5 family, uniquely expressed post-infection in the moderately resistant rice cultivar,
Tetep, compared to the susceptible check, IR 64. In this study, we isolated the OsTlp gene from Tetep and
used Agrobacterium-mediated transformation to introduce it into the local rice cultivar, MR 219, under a
constitutive promoter. We report the performance of several transgenic lines of MR 219, cultivated up to
the third generation (T3) in controlled conditions. Three independent T3 lines were selected for sheath blight
resistance analysis via artificial inoculation with R. solani at 45 days after sowing. Disease severity was
measured using relative lesion height (RLH) 30 days post-infection. Two promising transgenic lines (PL3
4 and PL6-1) exhibited enhanced tolerance, with average RLH values below 11%, while control plants
showed RLH ≥ 30%. Additionally, gene expression analysis via quantitative reverse transcription
polymerase chain reaction (qRT-PCR) demonstrated that OsTlp was overexpressed in the transgenic lines
by up to fivefold compared to those expressed in Tetep. These findings underscored the potential of genetic
engineering in enhancing rice resilience against sheath blight and addressing future food security
challenges.