Min Ni
 Associate Professor,
Department of Plant Biology
Ph.D., University of Oklahoma, 1992
Light signal transduction and seed development
Contact Information
Mailing Address:
Dr. Min Ni
Department of Plant Biology
University of Minnesota
250 Biological Sciences Center
1445 Gortner Avenue
St. Paul, MN 55108
Office: 644 Biological Sciences Center
Phone: 612-625-3702
Fax: 612-625-1738
E-mail: nixxx008@umn.edu
Web Site: Min Ni Lab
Research Interests
Our lab is currently focused on two separate research areas: light-regulated stomatal opening response and Arabidopsis seed development.
Drought is one of the major environmental factors that limit crop yield. The stomatal pores of plant leaves, situated in the epidermis and surrounded by a pair of guard cells, allow CO2 uptake for photosynthesis and the loss of water through transpiration. Blue light regulates the stomatal aperture in a natural environment and the signals are perceived by the blue/UV A light-absorbing phototropins and cryptochromes. The signaling components that link the perception of the blue light to the stomatal opening response are largely unknown, and hypersensitive to red and blue (hrb) mutants are of particular interest. The hrb mutants were initially isolated for their short hypocotyl phenotype under red and blue light. Interestingly, the blue light-induced stomatal opening response is also impaired in the hrb mutants, and the mutant plants are more resistant to dehydration and show reduced water loss and stomatal aperture. The strong stomatal phenotype of the hrb mutants may be due to impairment in both red and blue light signaling since red light often enhances blue light-specific responses. We have cloned HRB1 and mapped hrb2 and hrb3 to chromosomes 2 and 4, respectively. HRB1 encodes a nuclear ZZ-type zinc finger protein and HRB1 physically interacts with several nuclear proteins through its zinc finger domain. We are currently investigating the actions and interactions of HRBs with other components in light- and ABA-mediated stomatal movement signaling pathways, and identifying genes encoding HRB2 and HRB3. We are also studying the genetic and biochemical interactions of HRB1 with its putative interacting proteins. Our studies will open new possibilities to engineering stomatal activity and help plants to survive desiccation. The stomatal aperture is also regulated by other environmental cues such as drought in addition to blue light. Given that hrb plants may still respond to ABA, a well-known drought signal, these plants should enjoy the advantages of both constitutive and induced protection under water-limiting conditions.
Double fertilization in angiosperms leads to the formation of a diploid embryo and a triploid endosperm. Seed development in Arabidopsis then undergoes an initial phase of active endosperm proliferation followed by a second phase in which embryo grows at the expense of the endosperm. In many dicots, the embryo grows to full size and the mature seed contains only a single layer of endosperm cells. As the mature seed size is largely attained during the initial phase, the seed size is coordinately determined by the growth of the maternal ovule, endosperm, and embryo. The mechanisms underlying this control are still not well understood, yet seeds form the bulk of the diet of human population. We identify SHB1 as not previously described positive regulator of Arabidopsis seed development that operates through regulation of both cell size and cell number. shb1-D, a gain-of-function allele, increases seed size and shb1, a loss-of-function allele, reduces seed size. The increase in shb1-D seed size is associated with the timing of endosperm cellurization, enlargement of chalazal endosperm, and subsequent embryo development. SHB1 is required for the proper expression of MINI3 and IKU2, a WRKY transcription factor gene and an LRR receptor kinase gene, respectively. MINI3 has been shown by others to be required for the proper expression of IKU2, and mutation in either MINI3 or IKU2 retards endosperm development and reduces seed size (Luo et al., 2005). We have recently shown that SHB1 associates with MINI3 and IKU2 promoters in vivo and exists in a 323 kDa protein complex. We are currently searching for proteins that recruit SHB1 to the MINI3 and IKU2 promoters to control gene expression required for endosperm development. We are also identifying the components within the 323 kDa protein complex. Seed size is the yield trait that traditional breeding has had the most limited success in improving effectively and seed development in major seed crops such as soybean and canola follows a very similar path as Arabidopsis does. Enhancing the potential for large seed sizes represents one of the most promising and less explored avenues for significant increases in agricultural yields.
Selected Publications
Zhou Y., and Ni, M. (2009). SHB1 plays dual roles in photoperiodic and autonomous flowering. Developmental Biology (in press).
Zhou Y., Zhang, X., Kang, X., Zhao, X., Zhang, X., and Ni, M. (2009). SHORT HYPOCOTYL UNDER BLUE1 associates with MINISEED3 and HAIKU2 promoters in vivo to control Arabidopsis seed development. Plant Cell 21, 106-117.
Kang, X., Zhou, Y., Sun, X., and Ni, M. (2007). HYPERSENSITIVE TO RED AND BLUE 1 and its C-terminal regulatory function control FLOWERING LOCUS T expression. Plant Journal 52, 937-948.
Chen, M., and Ni, M. (2006). RED AND FAR-RED INSENSITIVE 2, a RING-domain zinc-finger protein, negatively regulates CONSTANS expression and photoperiodic flowering. Plant Journal 46, 823-833.
Kang, X., and Ni, M. (2006). Arabidopsis SHORT HYPOCOTYL UNDER BLUE 1 contains SPX and EXS domains and acts in cryptochrome signaling. Plant Cell 18, 921-934.
Chen, M., and Ni, M. (2006). RED AND FAR-RED INSENSITIVE 2, a RING-domain zinc-finger protein, mediates phytochrome-controlled seedling de-etiolation responses. Plant Physiology 140, 457-465.
Kang, X., Chong, J., and Ni, M. (2005). HYPERSENSITIVE TO RED AND BLUE 1, a ZZ-type zinc finger protein, regulates phytochrome B-mediated red and cryptochrome-mediated blue light responses. Plant Cell 17, 822-835.
Ni, M., Tepperman, J., and Quail, P.H. (1999). Binding of phytochrome B to its nuclear signaling partner PIF3 is reversibly induced by light. Nature 400, 781-784.
Ni, M., Tepperman, J., and Quail, P.H. (1998). PIF3, a phytochrome interacting factor necessary for photoinduced signal transduction, is a basic helix-loop-helix protein. Cell 95, 657-667.
Ni, M., Dehesh, K., Tepperman, J., and Quail, P.H. (1996). GT-2: In vivo transcriptional activation activity and definition of twin novel DNA-binding domains with reciprocal target-site selectivity. Plant Cell 8, 1041-1059.
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