in English
Osmotic stress signaling in Arabidopsis


Hiroaki Fujii, Senior Research Fellow
Matleena Punkkinen, DI. Doctoral Student


Plants must adjust to environmental perturbation. An understanding of the plant signaling pathways responding to osmotic stress is important for both basic science and agriculture, because drought and soil salinity are increasingly important problems. Since the mechanisms underlying how plants tolerate or fail to tolerate osmotic stress are complicated, many questions remain unanswered.

One important response to osmotic stress is the accumulation of the phytohormone abscisic acid (ABA), which induces several responses to osmotic stress. Exogenous application of ABA induces some parts of the gene expression that is induced by osmotic stress. On the other hand, some osmotic stress responses remain in ABA-insensitive mutants. Thus, osmotic stress signaling consists of an ABA-dependent and an ABA-independent pathway.

Osmotic stress signaling activates specific kinases, including one that belongs to the SNF1-related protein kinase (SnRK) 2 family, which is a plant-specific protein kinase family with 10 members (SnRK2.1-2.10) in Arabidopsis. ABA strongly activates SnRK2.2, 2.3, and 2.6, whereas osmotic stress activate almost all members of SnRK2s. Our previous achievements revealed that SnRK2.2, 2.3, and 2.6 are core components of the ABA pathways whereas SnRK2s are essential kinases for osmotic stress signaling. Though the activation mechanism of SnRK2s in the ABA pathway is elucidated, regulatory mechanisms of SnRK2s in the ABA-independent pathway remain obscure. Thus, further analysis of SnRK2s must be a key study to draw the whole signaling pathways.


We are looking for some novel components in the ABA-independent pathways. One is what regulates resistance to PP2C suppression. SnRK2.2, 2.3 and 2.6 are suppressed by protein phosphatase 2C (PP2C)s. Release from this suppression by ABA receptor PYR/PYLs is the key mechanism in the ABA pathway. In the ABA-independent pathway, there must be a mechanism releasing SnRK2s from PP2C-suppression independently from PYR/PYLs.  In addition, there should be regulators of SnRK2s. To find potential regulators of SnRK2s, we carried out some screening such as yeast two hybrid (Y2H) assay.


Barajas-Lopez JD, Moreno JR, Gamez-Arjona FM, Pardo JM, Punkkinen M, Zhu JK, Quintero FJ, Fujii H (2017) Upstream kinases of plant SnRKs are involved in salt stress tolerance Plant J. 93, 107–118, [A1]

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Ling, Y.; Alshareef, S.; Butt, H.; Lozano-Juste, J.; Li, L.; Galal, AA.; Moustafa, A.; Momin, AA.; Tashkandi, M.; Richardson, DN.; Fujii, H.; Arold, S.; Rodriguez, PL.; Duque, P. & Mahfouz, MM. 2016:  Pre-mRNA splicing repression triggers abiotic stress signaling in plants. - Plant J. 89, 291-309.   Free article   (Epub 2016 Sep 24).

Cui, F.; Brosché, M.; Lehtonen, MT.; Amiryousefi, A.; Xua, E.; Punkkinen, M.; Valkonen, JPT.; Fujii, H. & Overmyer, K. 2016:  Dissecting abscisic acid signaling pathways involved in cuticle formation. - MOLECULAR PLANT  9(6): 926-938.   (Epub 2016 Apr 7).
Allahverdiyeva, Y.; Battchikova, N.; Brosché, M.; Fujii, H.; Kangasjärvi, S.; Mulo, P.; Mähönen, AP.; Nieminen, K.; Overmyer, K.; Salojärvi J. & Wrzaczek, M. 2015:  Integration of photosynthesis, development and stress as an opportunity for plant biology. - NEW PHYTOLOGIST 208(3): 647-655.  Free article    (Epub 2015 Jul 14).
Cai,  Z.; Liu, JJ.; Wang, H.; Yang, C.; Chen,  Y.; Li, Y.; Pan, S.; Dong, R.; Tang,  G.; Barajas-Lopez, J.; Fujii, H. and Wang, X. 2014:  GSK3-like kinases positively modulate abscisic acid signaling through phosphorylating subgroup III SnRK2s in Arabidopsis. - PNAS 111(26): 9651-9656.   (Epub 2014 Jun 13).
Fujii, H. 2014:  Abscisic acid implication in plant growth and stress responses. - In:  Tran, LS. & Pal, S. (eds.) Phytohormones: A window to metabolism, signaling and biotechnological applications. - Springer Netherlands, 37-54, ISBN 978-1-4939-0491-4
Virlouvet, L.; Ding, Y.; Fujii, H.; Avramova, Z. & Fromm, M. 2014:  ABA signaling is necessary but not sufficient for RD29B transcriptional memory during successive dehydration stresses in Arabidopsis thaliana. - PLANT JOURNAL 79(1): 150-161.   (Epub 2014 May 7).
Fujii, H. & Zhu, JK. 2012:  Osmotic stress signaling via protein kinases. - CELLULAR AND MOLECULAR LIFE SCIENCES 69(19): 3165-3173.

PI´s previous publications

Fujii H, Verslues PE, Zhu JK (2011) Arabidopsis decuple mutant reveals the importance of SnRK2 kinases in osmotic stress responses in vivo. - Proc. Natl. Acad. Sci. U. S. A. 108, 1717-1722
Fujii H, Chinnusamy V, Rodrigues A, Rubio S, Antoni R, Park SY, Cutler SR, Sheen J, Rodriguez PL, Zhu JK (2009) In vitro reconstitution of an abscisic acid signaling pathway. - Nature 462, 660-664
Melcher K, Ng L, Zhou XE, Xu Y, Suino-Powell KM, Soon J, Park SY, Weiner JJ, Fujii H, Chinnusamy V, Kovach A, Li J, Wang Y, Li J, Peterson FC, Jensen DR, Yong EL, Volkman BF, Cutler SR, Zhu JK, Xu HE (2009) Crystal Structures of PYL1 and PYL2 Abscisic Acid Receptors Provide a Molecular Basis for Hormone Perception. - Nature 462, 602-608
Rohila JS, Chen M, Chen S, Chen J, Cerny RL, Dardick C, Canlas P, Fujii H, Gribskov M, Kanrar S, Knoflicek L, Stevenson B, Xie M, Xu X, Zheng X, Zhu JK, Ronald P, Fromm ME (2009) Protein-protein interactions of tandem affinity purified protein kinases from rice. - PLoS One. 4, e6685.
Park SY, Fung P, Nishimura N, Jensen DR, Fujii H, Zhao Y, Lumba S, Santiago J, Rodrigues A, Chow TF, Alfred SE, Bonetta D, Finkelstein R, Provart NJ, Desveaux D, Rodriguez PL, McCourt P, Zhu JK, Schroeder JI, Volkman BF, Cutler SR (2009) Abscisic acid inhibits type 2C protein phosphatases via the PYR/PYL family of ABA-binding START proteins. - Science 324, 1068-71.
Fujii H, Zhu JK (2009) An Arabidopsis mutant deficient in all three abscisic acid-activated protein kinases reveals critical roles in plant growth, reproduction and stress. - Proc. Natl. Acad. Sci. U. S. A. 106, 8380-8385
Ding X, Richter T, Chen M, Fujii H, Xie M, Zheng X, Kanrar S, Stevenson B, Dardick C, Li Y, Jiang H, Zhang Y, Yu F, Zhu L, Farmerie WG, Gribskov M, Zhu JK, Fromm ME, Ronald PC, Song WY (2009) A rice kinase-protein interaction map. - Plant Physiol. 149, 1478-1492
Fujii H, Zhu JK (2009) An autophosphorylation site of SOS2 is involved in salt tolerance in Arabidopsis. - Molecular Plant  2, 183-190
Kanaoka MM, Pillitteri LJ, Fujii H, Yoshida Y, Bogenschutz NL, Takabayashi J, Zhu JK, Torii KU. (2008) SCREAM/ICE1 and SCREAM2 Specify Three Cell-State Transitional Steps Leading to Arabidopsis Stomatal Differentiation. - Plant Cell. 20:1775-85
Batelli G, Verslues PE, Agius F, Qiu Q, Fujii H, Pan S, Schumaker KS, Grillo S, Zhu JK. (2007). SOS2 promotes salt tolerance in part by interacting with the vacuolar H+-ATPase and upregulating its transport activity. - Mol. Cell. Biol. 27: 7781-7790
Fujii H, Verslues PE, Zhu JK. (2007) Identification of two protein kinases required for ABA regulation of seed germination, root growth and gene expression in Arabidopsis. - Plant Cell. 19:485-494.
Sanchez-Barrena MJ, Fujii H, Angulo I, Martinez-Ripoll M, Zhu JK, Albert A. (2007) The structure of  the c-terminal domain of the protein kinase AtSOS2 bound to the calcium sensor AtSOS3. - Mol. Cell 26:427-435.
Agarwal M, Hao Y, Kapoor A, Dong CH, Fujii H, Zheng X, Zhu JK (2006) A R2R3-type MYB transcription factor is involved in the cold-regulation of CBF genes and in acquired freezing tolerance. - J. Biol. Chem. 281:37636-37645.
Fujii H, Chiou TJ, Lin SI, Aung K, Zhu JK. (2005) A miRNA invloved in phosphate starvation response in Arabidopsis. - Curr. Biol. 15:2038-2043.