Brassinosteroids-regulated nitrogen metabolism fine-tunes growth physiology and low nitrogen response in tomato

Abstract

Nitrogen (N) is a crucial nutrient for plants and its limited availability in the soils significantly affects plant growth and development. To adapt under low N condition, plants undergo various changes such as root system reprogramming to explore deeper soil horizons and metabolic activity adjustment. These N dependent responses and the genetic factors governing them are poorly known in crop plants. In this study, we investigated the effect of BRs on N metabolism in tomato. BRs application improved N assimilation and metabolic responses. By using the transgenic approach, we demonstrated the essential role of tomato Brassinazole resistant (BES1/BZR1) homolog 4 (BEH4) protein in regulating N metabolic response, growth physiology, and fruit quality. Overexpression of BEH4 promoted deeper root system architecture and improved physiological performance by adjusting N metabolic activity and photosynthetic efficiency in low N-grown plants. The BEH4 transgenic lines exhibited increased expression of genes involved in N uptake and assimilation which are associated with the improved N content and assimilation (root and shoot). Altogether, data suggested an essential role of BRs in plant adaptation to altered N regimes and appears potential target for genetic manipulation to improve nitrogen use efficiency (NUE) and nutritional quality in crops.