Regulation of ammonium acquisition and use in Oryza longistaminata ramets under nitrogen source heterogeneity

Abstract

Oryza longistaminata, a wild rice, vegetatively reproduces and forms a networked clonal colony consisting of ramets connected by rhizomes. Although water, nutrients, and other molecules can be transferred between ramets via the rhizomes, inter-ramet communication in response to spatially heterogeneous nitrogen availability is not well understood. We studied the response of ramet pairs to heterogeneous nitrogen availability using a split hydroponic system that allowed each ramet root to be exposed to different conditions. Ammonium uptake was compensatively enhanced in the sufficient-side root when roots of the ramet pairs were exposed to ammonium-sufficient and -deficient conditions. Comparative transcriptome analysis revealed that a gene regulatory network for effective ammonium assimilation and amino acid biosynthesis was activated in the sufficient-side roots. Allocation of absorbed nitrogen from the nitrogen-sufficient to the -deficient ramets was rather limited. Nitrogen was preferentially used for newly growing axillary buds on the sufficient-side ramets. Biosynthesis of trans-zeatin, a cytokinin, was up-regulated in response to the nitrogen supply, but trans-zeatin appeared not to target the compensatory regulation. Our results also implied that the O. longistaminata putative ortholog of rice (Oryza sativa) C-terminally encoded peptide1 (OsCEP1) plays a role as a nitrogen-deficient signal in inter-ramet communication, providing compensatory up-regulation of nitrogen assimilatory genes. These results provide insights into the molecular basis for efficient growth strategies of asexually proliferating plants growing in areas where the distribution of ammonium ions is spatially heterogeneous.

Plant growth and stress-regulating metabolite response to biochar utilization boost crop traits and soil health

“…For example, trans-zeatin promoted the ability of Arabidopsis thaliana plant to fine-tune its shoot growth to adapt to fluctuating environmental conditions ( Osugi et al., 2017 ). Our finding suggests that the high presence of zeatin under the BC-supplemented soil contributed to the increase in crop traits and the promotion of soil nutrients, especially N, NO 3 -N, and NH 4 -N. This behavior corroborates with a previous study ( Kawai et al., 2022 ), in which it was established that trans-zeatin biosynthesis belonging to cytokinin was significantly upregulated in response to the application of N. This finding also aligns with the results documented in the work of Kudo et al. (2012) , where cis-zeatin, a type of cytokinin, exhibited a physiological impact on rice growth and development.…”

The trans-zeatin-type side-chain modification of cytokinins controls rice growth

“…Nitrogen nutrition is one of the major environmental factors regulating CK biosynthesis, including tZ-type CK biosynthesis, for plant growth optimization ( Takei et al 2001b ; Kamada-Nobusada et al 2013 ; Ohashi et al 2017 ; Osugi et al 2017 ; Maeda et al 2018 ; Sakakibara 2021 ; Shibasaki et al 2021 ; Kawai et al 2022 ). In Arabidopsis, CYP735As are upregulated by the nitrate-specific signal and play a crucial role in nitrate-induced accumulation of tZ-type CKs ( Engelsberger and Schulze 2012 ; Maeda et al 2018 ).…”

Insights on Phytohormonal Crosstalk in Plant Response to Nitrogen Stress: A Focus on Plant Root Growth and Development

“…Recent studies have revealed that when roots are exposed to various nitrate sources, C-TERMINALLY ENCODED PEPTIDE 1 ( CEP1 ), CEP RECEPTOR ( CEPR ), and CEP DOWNSTREAMS ( CEPDs ) play key roles in regulating NRT2.1 ( Figure 1 ) [ 67 ]. CEPDL2 can transport from the phloem to the cortex cells when NRT2.1 is expressed after CEP1/2 and CEPDL2 have moved from shoot to root through the phloem [ 68 ].…”