Excess Nitrogen Responsive HvMADS27 Transcription Factor Controls Barley Root Architecture by Regulating Abscisic Acid Level

Nitrogen (N) is an important element for plant growth and development. Although several studies have examined plants' response to N deficiency, studies on plants' response to excess N, which is common in fertilizer-based agrosystems, are limited. Therefore, the aim of this study was to examine the response of barley to excess N conditions, specifically the root response. Additionally, genomic mechanism of excess N response in barley was elucidated using transcriptomic technologies. The results of the study showed that barley MADS27 transcription factor was mainly expressed in the roots and its gene contained N-responsive -regulatory elements in the promoter region. Additionally, there was a significant decrease in expression under excess N condition; however, its expression was not significantly affected under low N condition. Phenotypic analysis of the root system of knockdown and overexpressing barley plants revealed that HvMADS27 regulates barley root architecture under excess N stress. Further analysis of wild-type (WT) and transgenic barley plants ( and ) revealed that HvMADS27 regulates the expression of HvBG1 β-glucosidase, which in turn regulates abscisic acid (ABA) level in roots. Overall, the findings of this study showed that expression is downregulated in barley roots under excess N stress, which induces expression, leading to the release of ABA from ABA-glucose conjugate, and consequent shortening of the roots.