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People

Current Lab Members

Dr. Sheng Luan, Principal Investigator email

Dr. Renjie Tang, Post doc email

Dr. Xin Hou, Post doc email

Yangping Li, Visiting Scholar email

Rania Belal, Visiting Graduate Student email

Qing Ma, Visiting Scholar email

Xiaojiang Zheng, Visiting Scholar email

Weimin Jiang, Visiting Scholar email

Congcong Hou, Visiting Scholar email

Veder Garcia, Graduate Student email

Tom Kleist, Graduate Student email

Gregory Mathews, Graduate Student email

 
Former Lab Members

 

See us! Please click ---> here <--- .
   

 Research Projects

 

Signal Transduction and Chloroplast Biology

  Our goal is to understand the molecular mechanism underlying plant response and adaptation to its environment. Because higher plants can not “walk away” from their environment, they have evolved elaborate mechanisms to integrate their outside world into the program of their life cycle control. When environmental conditions change, plants rapidly perceive those changes and respond by physiological and developmental changes that would help themselves adapt to the “new” environment. We are interested in revealing the molecular networks that connect the environmental input to the intracellular responses in plants. The understanding of biochemical pathways that allow plants to adapt to constantly changing environment is also among our primary research goals.

Current Projects 

Environmental Sensing Using Ca2+ as a Ubiquitous Messenger

Upon environmental changes, a plant cell has a number of rapid responses. One of these is fluctuation of cellular Ca2+ that is often required for the further downstream responses and is thus referred to as a “second messenger”. A critical question regarding calcium signaling is how a simple cation serves as a messenger for so many different signals leading to distinct responses. The key step is signal “sensing”, i.e., the calcium signal is sensed by proteins functioning as Ca2+ sensors. These sensors bind Ca2+ and change their conformation/function. We have recently uncovered a family of novel Ca2+ sensors (CBLs) from Arabidopsis. The CBL-type Ca2+ sensors function by interacting with and regulating a family of protein kinases (CIPKs) in a number of signaling pathways. At least 10 members of CBLs interact with 25 CIPKs, forming a large number of molecular complexes that interpret the calcium signals in plant cells. The functional specificity, synergism, and antagonism among various CBLs and CIPKs constitute a complex signaling network for cellular regulation and crosstalk.

CBL-CIPK in nutrient sensing: Plants are growing in a nutrient-poor environment especially after a long history of farming. Agricultural production is heavily relying on the application of chemical fertilizers, opposing a serious economic and environmental problem worldwide. One solution would be to breed crops that can tolerate low-nutrient soils without the need of fertilizers. Recent work in Luan laboratory identified a CBL-CIPK signaling pathway that regulates the activity of a voltage-gated potassium channels involved in K-uptake in plant roots. Manipulation of CBL-CIPK network can therefore enhance the growth of plants under low-K soils, impacting agriculture and environment.

CBL-CIPK in stress and ABA responses: Several CBL-CIPK pathways have been identified that function in plant responses to environmental stress conditions including salt, drought, and cold. CBL-CIPK network is also involved in the response to plant hormones such as ABA that regulates stress responses. The crosstalk and interaction among the CBLs and CIPKs form a complex signaling network that  links environmental responses to biochemical processes in plant cells. 

Environmental Adaptation through Metabolic Regulation in the Chloroplast

After environmental signals are perceived and interpreted by signaling pathways, plant cells respond to the signals by biochemical and physiological changes downstream of the signaling process. Many of the biochemical changes in plants involve metabolic processes in the chloroplasts that serve as a critical “factory” for plant productivity. The best known photosynthetic process include both light harvesting by the photosystems and carbon fixation. As the most important metabolic process, photosynthetic activity and its regulated are connected to all environmental changes. Although the basic biochemical pathways are largely known, the regulatory pathways that link the environmental signals to the light and dark reactions are poorly understood.  Luan laboratory focus on the mechanisms underlying regulation of photosynthetic activity by environmental signals. 

Light reaction and bio-energy conversion:  We are interested in the mechanism of assembly and maintenance of the photosystems that harvest light energy and convert it into the chemical forms. Our recent studies have discovered a family of protein foldases and chaperones (called immunophilins) in the chloroplast  that function in the assembly and maintenance of photosynthetic electron transport complexes.  Because maintaining the function of photosynthetic complexes is one of the limiting factors in photosynthetic activity, our findings on the immunophilins in the chloroplast will provide information for enhancing light energy conversion by plants.

Dark Reaction and Biomass: The output of photosynthetic carbon fixation is transitory starch in the chloroplast. The starch biosynthesis and degradation is under tight control by environmental factors such as light-dark cycle and stress conditions.  Although regulation of glycogen (starch) metabolism is well understood in animal cells, our understanding of metabolic regulation of starch accumulation is still in its infancy.  Recent research in Luan laboratory identified a protein phosphatase (DSP4) that plays a central role in regulating starch accumulation in Arabidopsis chloroplasts, providing a strong evidence that protein phosphorylation is involved in starch regulation. In addition, the DSP4 activity is regulated by redox states that are controlled by light-dark transition. Therefore DSP4 may provide a molecular link between diurnal cycle and starch accumulation. As starch is one of the most abundant  plant-derived polymers, its sheer biomass and ease of production make it a critical source for biofuel production. Understanding the regulatory mechanism for starch accumulation in plants will directly impact the biomass production and biofuel industry.

Recent Publications

Tang RJ, Liu H, Yang Y, Yang L, Gao XS, Garcia VJ, Luan S*, Zhang HX* (2012) Tonoplast calcium sensors CBL2 and CBL3 control plant growth and ion homeostasis through regulating V-ATPase activity in Arabidopsis. Cell Res 22: 1650-1665.

Lee SC, Lim CW, Lan W, He K, Luan S (2012) ABA signaling in guard cells entails a dynamic protein-protein interaction relay from the PYL-RCAR family receptors to ion channels. Mol Plant (in press).

Yu F, Qian L, Nibau C, Duan Q, Kita D, Levasseur K, Li X, Lu C, Li H, Hou C, Li L, Buchanan BB, Chen L, Cheung AY, Li D, Luan S (2012) FERONIA receptor kinase pathway suppresses abscisic acid signaling in Arabidopsis by activating ABI2 phosphatase. Proc Natl Acad Sci USA 109: 14693-14698.

Meng L, Buchanan BB, Feldman JJ, Luan S (2012) A putative nuclear CLE-like (CLEL) peptide precursor regulates root growth in Arabidopsis. Mol Plant 5: 955-957.

Vasudevan D, Fu A, Luan S, Swaminathan K (2012) Crystal structure of Arabidopsis cyclophilin38 reveals a previously uncharacterized immunophilin fold and a possible autoinhibitory mechanism. Plant Cell 24: 2666-2674.

Li S, Yu J, Zhu M, Zhao F, Luan S (2012) Cadmium impairs ion homeostasis by altering K+ and Ca2+ channel activities in rice root hair cells. Plant Cell Environ 35: 1998-2013.

Fu A, Liu H, Yu F, Kambakam S, Luan S, Rodermel S (2012) Alternative oxidases (AOX1a and AOX2) can functionally substitute for plastid terminal oxidase in Arabidopsis chloroplasts. Plant Cell 24: 1579-1595.

Meng L, Buchanan BB, Feldman JJ, Luan S (2012) CLE-like (CLEL) peptide s control the pattern of root growth and lateral root development in Arabidopsis. Proc Natl Acad Sci USA 109: 1760-1765.

Lee SC, Luan S (2012) ABA signal transduction at the crossroad of biotic and abiotic stress responses. Plant Cell Environ 53-60.

Li H, Luan S. (2011) The Cyclophilin AtCYP71 Interacts with CAF-1 and LHP1 and Functions in Multiple Chromatin Remodeling Processes. Mol Plant. 4, 748-58.

Lan WZ, Lee SC, Che YF, Jiang YQ, Luan S. (2011) Mechanistic analysis of AKT1 regulation by the CBL-CIPK-PP2CA interactions. Mol Plant 4(3):527-36.

Ahn JC, Kim DW, You YN, Seok MS, Park JM, Hwang H, Kim BG, Luan S, Park HS, Cho HS. (2010) Classification of rice (Oryza sativa L. Japonica nipponbare) immunophilins (FKBPs, CYPs) and expression patterns under waterstress. BMC Plant Biol. 10:253.

Li H, Luan S. (2010) P53 is a histone chaperone required for repression of ribosomal RNA gene expression in Arabidopsis. Cell Res. 20, 357-66.

Cheong YH, Sung SJ, Cho JS, Luan S. (2010) Constitutive overexpression of the calcium sensor CBL5 confers osmotic or drought stress tolerance in Arabidopsis. Mol Cells. 29, 159-65.

Lan, W., Wang, W., Buchanan, BB. and Luan, S. (2010) A Rice HKT-type transporter conceals a calcium-permeable cation channel. Proc. Natl. Acad. Sci. USA. 107, 7089-94.

Yu F, Shi J, Zhou J, Gu J, Chen Q, Li J, Cheng W, Mao D, Tian L, Buchanan BB, Li L, Chen L, Li D, Luan S. (2010) ANK6, a mitochondrial ankyrin repeat protein, is required for male-female gamete recognition in Arabidopsis thaliana. Proc Natl Acad Sci U S A. 107, 22332-7.

Wu, W-H., Wang, Y., Lee, S.C., Lan, W., Luan, S. (2010) Regulation of ion channels by the calcium signaling network in plant cells. Book Chapter in Ion Channels and Plant Stress Responses Book edited by V. Demidchik and F. Maathuis; Springer Publishing Inc.

Chae, L., Cheong, Y., Kim, K., Pandey, G., Luan, S. (2010) Protein Kinases and Phosphatases for Stress Signal Transduction in Plants. Book Chapter in Abiotic Stress Adaptation in Plants Book edited by Pareek, et al. Springer Publishing Inc.

Chae L, Sudat S, Dudoit S, Zhu T, Luan S. (2009) Diverse Transcriptional Programs Associated with Environmental Stress and Hormones in the Arabidopsis Receptor-Like Kinase Gene Family. Mol Plant. 2, 84-107.

Sun SY, Chao DY, Li XM, Shi M, Gao JP, Zhu MZ, Yang HQ, Luan S, Lin HX (2009) OsHAL3 mediates a new pathway in the light-regulated growth of rice. Nat Cell Biol. 11, 845-51.

Luan, S. (2009) The CBL-CIPK network in plant calcium signaling. Trends in Plant Sci. 14(1):37-42.

Luan, S., Lan, W., and S-C, Lee (2009) Potassium nutrition, sodium toxicity, and calcium signaling: connections through the CBL-CIPK network. Curr. Opin. Plant Biol. 12, 339-346.

Click here to see older publications


Reviews and Book Chapters

Luan, S. (2003) Protein phosphatases in plants. Annu. Rev. Plant Biol. 54, 69-90.

Luan,S., Kudla, J., Gruissem, W. (2002) Calmodulins and calcineurin B-like proteins: calcium sensors for specific signal response coupling in plants.Plant Cell 14, 389-400.

Luan, S. (2002) Tyrosine phosphorylation in plant cell signaling. Proc. Natl. Acad. Sci. USA. 99, 11567-11569.

Luan, S. (2001) Signaling Drought in Guard Cells. Plant Cell Environment 25, 229-237.

Luan, S., Gupta, R., and Ting, T. (2001) Tyrosine phosphatases in higher plants. New Phytol. 151, 155-164.

Luan, S. (1999) Plant protein phosphatases. In "Plant Protein Phosphorylation" Ed. M. Kreis and J.C. Walker. Academic Press (London, UK).

Luan, S. (1998) Protein phosphatases and plant signaling cascades. Trends Plant Sci. 3, 271-275.

Luan, S. (1998) Immunophilins in animals and higher plants. Bot. Bull. Acad. Sin. 39, 217-223.

Luan, S. (1998) Protein phosphatases in higher plants. Acta Bot. Sin. 40, 883-889.

 


Protocols

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