Transcriptome analysis of Arabidopsis shoots and roots whose nitrate levels and IPT3 expression are manipulated in a shoot-specific manner

In plants, nitrate is suggested to act as an indicator of nitrogen (N) status that modulates N responses under steady-state conditions. Our preceding study suggested that shoot nitrate accumulation alone represses expression of N starvation-inducible genes in shoots and roots. Notably, we observed that shoot nitrate accumulation was accompanied by increases in shoot expression of ISOPENTENYL TRANSFERASE 3 (IPT3) and shoot levels of N6-(?2-isopentenyl) adenine (iP)-type CK. IPT3 expression is localized primarily in phloem companion cells, and iP-type CKs, which are synthesized by IPT3, are phloem-mobile. Hence, both local and systemic responses to shoot nitrate status may be regulated by IPT3-synthesized iP-type CKs. Thus, the present study aims to dissect the local/systemic responses to shoot nitrate status and their dependence on shoot IPT3. To achieve this, we developed a novel experimental system to manipulate nitrate levels and IPT3 expression in a shoot-specific manner using grafted plants derived from the plants lacking nitrate reductase and/or IPT3. Using shoots and roots from the grafted plants, RNA-seq analysis was performed.