Cytokinins are involved in the regulation of many plant growth and development processes, and function in response to abiotic stress. Cytokinin signaling is similar to the prokaryotic two-component signaling systems and includes the transcriptional upregulation of type-A response regulators (RRs), which in turn act to inhibit cytokinin signal response via negative feedback. Cytokinin signaling consists of several gene families and only a handful full of genes is studied. In this study, we demonstrated the function of two highly identical type-A RR genes from rice, OsRR9 and OsRR10, which are induced by cytokinin and only OsRR10 repressed by salinity stress in rice. Loss-of-function mutations give rise to mutant genes, osrr9/osrr10, which have higher salinity tolerance than wild type rice seedlings. The transcriptomic analysis uncovered several ion transporter genes, which were upregulated in response to salt stress in the osrr9/osrr10 mutants relative to the wild type seedlings. These include high-affinity potassium transporters, such as OsHKT1;1, OsHKT1;3 and OsHKT2;1, which play an important role in sodium and potassium homeostasis. In addition, disruption of the genes OsRR9 and OsRR10 also affects the expression of multiple genes related to photosynthesis, transcription and phytohormone signaling. Taken together, these results suggest that the genes OsRR9 and OsRR10 function as negative regulators in response to salinity in rice.
The phytohormone cytokinin plays a significant role in nearly all aspects of plant growth and development. Cytokinin signaling has primarily been studied in the dicot model Arabidopsis, with relatively little work done in monocots, which include rice (
- NSF-PAR ID:
- 10452928
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- The Plant Journal
- Volume:
- 106
- Issue:
- 1
- ISSN:
- 0960-7412
- Page Range / eLocation ID:
- p. 159-173
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Summary Cytokinins control critical aspects of plant development and environmental responses. Perception of cytokinin ultimately leads to the activation of proteins belonging to the type‐B Response Regulator family of cytokinin response activators. In
Arabidopsis thaliana , ARR1 is one of the most abundantly expressed type‐B Response Regulators.We investigated the link between cytokinin signaling, protein synthesis, plant growth and osmotic stress tolerance.
We show that the increased cytokinin signaling in ARR1 gain‐of‐function transgenic lines is associated with increased rates of protein synthesis, which lead to growth inhibition and hypersensitivity to osmotic stress. Cytokinin‐induced growth inhibition and osmotic stress hypersensitivity were rescued by treatments with ABA, a hormone known to inhibit protein synthesis. We also demonstrate that cytokinin‐induced protein synthesis requires isoforms of the ribosomal protein L4 encoded by the cytokinin‐inducible genes
RPL4A andRPL4D , and thatRPL4 loss‐of‐function increases osmotic stress tolerance and decreases sensitivity to cytokinin‐induced growth inhibition.These findings reveal that an increase in protein synthesis negatively impacts growth and osmotic stress tolerance and explain some of the adverse effects of elevated cytokinin action on plant development and stress physiology.
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