Authors: Anshul Watts1, Archana Watts2, Kishor U Tribhuvan1, Era Vaidya Malhotra3 and Rajendra Prasad Meena1
1 ICAR-National Research Centre On Plant Biotechnology, New Delhi-110012
2 ICAR-Division of Plant Physiology, Indian Agriculture Research Institute, New Delhi-110012
3ICAR-National Bureau of Plant Genetic Resources, New Delhi-110012
Abstract:
Cell to cell communication is essential for transportation of various signaling molecules, proteins, small RNA and transcription factors. Plant cell communicate each other through Plasmodesmata.
Introduction
Different organisms communicate with each other through different means; for different purposes and this communication is essential for their survival. Like the communication between organisms, cells also communicate with each other at the cellular level for cellular fate and organismal development. The ways and means of cellular communication vary with cell type and organism to which the cells belong. Cell to cell communication in plant cells is different from that in animal cells. Plant cells communicate with each other through pores connecting neighboring cells, known as plasmodesmata. Plasmodesmata connects the endoplasmic reticulum (ER) of adjacent cells through desmotubule. Plasmodesmata are analogous to gap junctions and tunneling nanotubes of animals. The major functions of plasmodesmata are transporting of signaling molecules, various transcription factors, proteins, peptides and small RNAs from one cell to another cell. Thus, it has a key role in plant growth and development and provides defense against pathogen attack. Disruption of cell-cell communication has serious impact on plant growth and development. Some of the key class of molecules which move through plasmodesmata are as follows:
Transcription factors
Transcription factors are among the important proteins involved in growth and development of organisms and it is essential to transport them from one cell to another cell for their appropriate functions. Knotted 1 transcription factor of maize was the first transcription factor found to be selectively traffic through plasmodesmata. Subsequent studies revealed a number of transcription factors which move from cell to cell. Some of the transcription factors which move selectively from cell to cell are listed in Table 1. Chaperonin (proteins which help in correct folding of other proteins) plays a key role in cell to cell movement of transcription factors.
Table 1. Transcription factors and their movement
| Transcription factor | Movement | References |
| SHOOTMERISTEMLESS (STM) | Epidermal L1 to inner layer | Kim, J.Y., et.al. 2003 |
| KNAT1/BREVIPEDICELLUS | Epidermal L1 to inner layer | Kim, J.Y., et.al. 2003 |
| SHORTROOT (SHR) | Stele cells to endodermis | Nakajima K., et.al. 2001 |
| LEAFY (LFY) | Intercellular movement | Sessions A., et.al. 2000 |
| DEFICIENS (DEF) | Epidermal inner L2 or L3 to L1 | Perbal, M.C., et.al. 1996 |
| GLOBOSA (GLO) | Epidermal inner L2 or L3 to L1 | Perbal, M.C., et. al. 1996 |
Small RNAs
Small RNAs move short distances to the neighboring cells as well as long distances from one tissue to another. This movement of small RNAs is required when the small RNAs are produced in cells other than the target cells or tissues, for example, small RNA produced in top of the leaf move from top to the bottom of the leaf and determine leaf pattern. miR165/166 produced in root cells move to other adjacent cells, and their movement is essential for determining vascular cell types. Similarly, upon viral infection certain small RNA are produced and move from one cell to another cell which further play a critical role in providing viral resistance.
Peptides and signaling molecules
Initially it was thought that peptides can act as a signaling molecule in animals only. But with the discovery systemin as the first plant signaling molecule playing an important role in defense, was demonstrated that peptides can also act as signaling molecules in plants. Further a number of peptide molecules have been discovered in plants which act as signaling molecules, like Clavata-3, which plays an important role in apical meristem maintenance; inflorescence deficient in abscission (IDA) play a critical role in abscission; Epidermal Patterning Factor (EPF) have role in stomatal development. Based on structure, peptide signaling molecules have been divided into two classes; Class I comprising of the cysteine rich peptides and the Class II comprising of cysteine poor peptides.
Conclusion
Cell to cell communication is essential for proper growth and development of plants and also has a significant role in various stresses. Plasmodesmata are the key players through which various transcription factors, signaling molecules, small peptides and RNA can move from one cell to other cell. Short distance as well as long distance movement of various molecules throughout the various plant developmental stages is necessary. However, still many aspects of cell to cell communication remain to be elucidated.
References:
• Brunkard JO, Runkel AM, Zambryski PC. (2013). Plasmodesmata dynamics are coordinated by intracellular signaling pathways. Curr Opin Plant Biol 16, 614â€"620.
• Dunoyer P, Melnyk CW, Molnar A, Slotkin RK. (2013). Plant mobile small RNAs. Cold Spring Harb Perspect Biol 5, a017897.
• Kim, J.Y., Yuan, Z., and Jackson, D. (2003). Developmental regulation and significance of KNOX protein trafficking in Arabidopsis. Development 130, 4351â€"4362.
• Murphy E, Smith S, De Smet I. (2012). Small signaling peptides in Arabidopsis development: how cells communicate over a short distance. Plant Cell 24, 3198â€"3217
• Nakajima, K., Sena, G., Nawy, T., and Benfey, P.N. (2001). Intercellular movement of the putative transcription factor SHR in root patterning. Nature 413, 307â€"311.
• Perbal, M.C., Haughn, G., Saedler, H. and Schwarz-Sommer, Z. (1996). Non-cell-autonomous function of the Antirrhinum floral homeotic proteins DEFICIENS and GLOBOSA is exerted by their polar cell-to-cell trafficking. Development 122, 3433â€"3441.
• Sessions, A., Yanofsky, M.F., and Weigel, D. (2000). Cell-cell signaling and movement by the floral transcription factors LEAFY and APETALA1. Science 289, 779â€"781.
About Author / Additional Info:
I am currently a scientist at National Research Centre On plant Biotechnology, Pusa Campus, New Delhi-110012