Thioredoxins as Molecular Players in Plants, Pests, and Pathogens

Throughout their life cycle, plants are exposed to various kinds of biotic and abiotic stress conditions. Plant responds to such stressors through the orchestrated machinery at the molecular level and exerts its defense. Plants have sophisticated mechanisms to sense environmental cues, which guard them to mount a protective response. The antioxidant machinery in the plants comprises enzymatic and non-enzymatic proteins. The enzymatic proteins include glutaredoxins, thioredoxins, and many others. Thioredoxin (Trx) are multifunctional small redox proteins found in every living organism, and various Trxs have been identified in plants. The two reactive cysteine residues are found in the conserved motif of thioredoxins. They play post-translational regulatory role in number of cellular processes such as oxidative stresses and plant pathogen interactions. Trxs are reduced by NADP-thioredoxin reductase (NTR) in the presence of NADPH. In model plant, Arabidopsis thaliana, At Trxs are pathogen-inducible and contribute towards plant defense via expression of the defense responsive pathogenesis-related (PR) genes. The most important family of thioredoxin proteins is Trxh, having their role in many versatile processes including defense responses in plants. We present upcoming, prospective roles of thioredoxin proteins of plants, insects as well as pathogens and their role in biological interactions. This chapter would assist plant scientists in further exploring the crucial role of thioredoxins in response to attack by the insects causing losses to economically important plants.