Zheng Lab: Nutrient Balance Signaling Networks in Plants

 

Exciting breakthrough:

A novel nutrient sensor identified!

SULTR1;2 final.pub.white.png

 

 

 

 

 

 

 

 
PI: Zhi-Liang Zheng (PhD, 1999, Ohio State University)

 

Associate Professor

Department of Biological Sciences

Lehman College, City University of New York

250 Bedford Park Blvd. West

Bronx, NY 10468

 

Office: 2404 Science Hall

Lab: 2401 Science Hall

(718) 960-6955 (Office)

(718) 960-5741 (Lab)

(718) 960-8236 (Fax)

Predicted 3D

structure of SULTR1;2

 
E-mail: zhiliang.zheng@lehman.cuny.edu

 

Teaching

 

BIO 238 Genetics (undergraduate level, 4 credits: 2-hr lecture, 4-hr lab)

BIO 501 Special Topics in Genetics (graduate level, 4 credits: 4-hr lecture)

 

Research

 

Plants are non-motile, photoautotrophic organisms and therefore they must respond and adapt to the constantly changing environments (such as light, temperature, water, CO2 and nutrients). Nutrient availability is one of the most critical factors that limit plant growth and crop yield. Because of the lack of knowledge that governs how much and when mineral nutrients should be applied to crops, farmers tend to apply excessive amounts of fertilizers, which in turn negatively impacts ecosystems and environments. Therefore, in order to improve the nutrient use efficiency and optimize the application of fertilizers, it is critical to dissect the fine-tuned but complex nutrient perception and signal transduction networks. Our research is currently focused on the major nutrients such as carbon (C), nitrogen (N) and sulfur (S), with the following specific aims:

 

OSU1-mediated C/N balance signaling Cellular C and N metabolism must be tightly coordinated to sustain optimal plant growth and development at the molecular and whole plant systems levels. Furthermore, C/N balance is also critical for the ecosystem response to elevated atmospheric CO2. Despite numerous physiological and molecular studies in C/N balance or ratio response, very few genes have been shown to play important roles in C/N balance signaling.

 

Using a genetic approach, we recently identified a novel gene (OVERSENSITIVE TO SUGAR1, OSU1) involved in C/N balance response in Arabidopsis thaliana (Gao et al., 2008). Mutations in the OSU1 gene result in the hypersensitivity of the seedlings to the imbalanced C/N (high C/low N, and low C/high N), but the osu1 mutants respond normally as wild-type under the balanced C/N, low C/low N and high C/high N. OSU1 encodes a putative AdoMet-dependent methyltransferase. Interestingly, osu1 mutants are allelic to qua2/tsd2, the cell-adhesion-defective mutants reported by two other groups (Mouille et al., 2007; Krupkova et al., 2007). This indicates that OSU1/QUA2/TSD2 might either have distinct substrates in the control of cell adhesion and C/N balance response or is important in linking cell wall biogenesis and C/N balance response. We are currently investigating its signaling mechanisms in the C and N nutrient balance response.

 

Novel components in S nutrient sensing and C-N-S cross-talk  Through a C, N and S combinatorial design, we have revealed that activation of a vacuolar sulphate transporter gene (SULTR4;2) and a putative b-glucosidase 28 (BGLU28) gene by sulfur (S) deficiency is primarily dependent on the C availability which interacts synergistically with N (Dan et al., 2007). This demonstrates the differential effects of C, N and S nutrients on gene expression. To understand the regulatory mechanism, we have taken advantage of this novel nutrient regulatory pattern to identify nutrient sensing/signaling proteins involved in the C-N-S cross-talk. Genetic, physiological and molecular approaches will be used to understand how plants sense the nutrient status and cross-talk to optimize the opportunity for cellular metabolism, growth and development.

 

Using the BGLU28:GUS reporter-based mutant screen, we have identified two novel alleles (sel1-15 and sel1-16) of the Arabidopsis high affinity transporter SULTR1;2 in which sulfate uptake was inhibited and gene expression was enhanced (Zhang et al., 2014). However, the sensitivity in sulfur-induced down-regulation for several genes known to affect S nutrient response was reduced in sel1-15 and sel1-16 alleles even if the internal S status was similar between wild-type and the mutant alleles. This genetic evidence indicates that SULTR1;2 has a dual role in sulfate transport and sensing, which may be classified as a transporting receptor or “transceptor”. We are currently working on the mechanism by which SULTR1;2 senses the sulfur nutrient status and how this signal is transmitted to the nucleus. One of the intriguing features of SULTR1;2 is that G208, which is mutated to D208 in sel1-16, is located on transmembrane helix 5 (TM5) and is highly conserved among all transporters related to SULTR1;2 from plants to yeast and animals (Zheng et al., 2014).

 

Role of hormones in nutrient signaling Plant hormones play an important role in modulating intracellular and intercellular responses to both internal and external nutrient status. We have shown that auxin, the key hormone in plants, plays a negative regulatory role in part of sulphate deficiency response (Dan et al., 2007). Furthermore, abscisic acid (ABA), a “master” stress hormone, likely has a similar negative role in part of S deficiency response. Our previous functional genomics work suggests that the low dose ABA-specific activation of some regulatory genes is gated by the ROP10 small GTPase, a negative regulator of ABA signaling (Xin et al., 2005). Taken together, these results indicate that plant hormones likely facilitate plant cells to closely monitor the fluctuations in nutrient status during growth and development. We are investigating the role of other hormones in nutrient status sensing and signaling.

 

Control of cytoskeletal organization in root hair-mediated nutrient uptake and response Root hairs are important for both the anchorage of the root system to the soil and the uptake of water and nutrients, although they are not essential for plant growth and development. Root hairs are long, thin tubular-shaped outgrowths from root epidermal cells called trichoblasts. Root hair tip growth is one of the few extreme types of highly dynamic, polarized growth, and has been used as a unique model system for the study of plant cell polarity. This dynamic process requires the well-coordinated cytoskeletons, such as actin filaments (AF) and microtubules (MT), to facilitate active organelle and vesicle transport. Constitutive activation of ROP2 and other members of ROP GTPases have been shown to disrupt the root hair tip growth, likely as a result of the alteration in AF and MT organizations. Interestingly, the tip growth defect caused by the constitutive activation of ROP2 can be enhanced by increasing concentrations of C, indicating a link between the cytoskeletal organization and nutrient response. To identify novel components of the ROP2-regulated MT and AF cross-talk, we have used a forward genetic approach, together with cell biological and biochemical tools, to understand how ROP2 and a kinesin called MRH2 act to control the MT organization and coordinate with AF (Yang et al., 2007).

 

Selected Publications

 

  

Zheng Z-L, Zhang B, Leustek T (2014)  

Transceptors at the boundary of nutrient transporters and receptors: A new role for Arabidopsis SULTR1;2 in sulfur sensing.

Frontiers in Plant Science 5:710

 

Zhang B, Pasini R, Dan H, Joshi N, Zhao Y, Leustek T, Zheng Z-L (2014)

Aberrant gene expression in the Arabidopsis SULTR1;2 mutants suggests a possible regulatory role for this sulfate transporter in response to sulfur nutrient status.

Plant Journal 77:185-197

 

Zheng Z-L (2009)

Carbon and nitrogen nutrient balance signaling in plants.

Plant Signaling & Behavior 4: 584-591

 

Xin Z, Wang A, Yang G, Gao P and Zheng Z-L (2009)

The Arabidopsis A4 subfamily of lectin receptor kinases negatively regulates abscisic acid response in seed germination.

Plant Physiology 149: 434-444

 

Gao P, Xin Z and Zheng Z-L (2008)

The OSU1/QUA2/TSD2-encoded putative methyltransferase is a critical modulator of carbon and nitrogen nutrient balance response in Arabidopsis.

PLoS ONE 3: e1387

 

Yang G, Gao P, Zhang H, Huang S and Zheng Z-L (2007)

A mutation in MRH2 kinesin enhances the root hair tip growth defect caused by constitutively activated ROP2 GTPase in Arabidopsis.

PLoS ONE 2: e1074

 

Dan H, Yang G and Zheng Z-L (2007)

A negative regulatory role for auxin in sulphate deficiency response in Arabidopsis thaliana.

Plant Molecular Biology 63: 221-235

 

Xin Z, Zhao Y and Zheng Z-L (2005)

Transcriptome analysis reveals specific modulation of abscisic acid signaling by ROP10 small GTPase in Arabidopsis.

Plant Physiology 139: 1350-1365

 

Fu Y, Gu Y, Zheng Z-L, Wasteneys G and Yang Z (2005)

Arabidopsis interdigitating cell growth requires two antagonistic pathways with opposing action on cell morphogenesis.

Cell 120: 687-700

 

Zheng Z-L, Nafisi M, Tam A, Li H, Crowell DN, Chary SN, Shen J, Schroeder JI and Yang Z (2002)

Plasma membrane-associated ROP10 small GTPase is a specific negative regulator of abscisic acid responses in Arabidopsis.

Plant Cell 14: 2787-2797

 

Li H, Shen J, Zheng Z-L, Lin Y and Yang Z (2001)

The Rop GTPase switch controls multiple developmental processes in Arabidopsis.

Plant Physiology 126: 670-684

 

Zheng Z-L, Yang Z, Jang J-C and Metzger JD (2001)

Modification of plant architecture in chrysanthemum by ectopic expression of the tobacco phytochrome B1 gene.

Journal of the American Society for Horticultural Sciences 126: 19-26  (Won the American Society for Horticultural Sciences Most Outstanding Publication Award of 2001)

 

Zheng Z-L and Yang Z (2000)

The Rop GTPase switch turns on polar growth in pollen. 

Trends in Plant Sciences 5: 298-303

      

Zheng Z-L and Yang Z (2000)

The Rop GTPase: an emerging signaling switch in plants.

Plant Molecular Biology 44: 1-9