A Cell Wall Extract from Piriformospora indica Promotes Tuberization in Potato (Solanum tuberosum L.) Via Enhanced Expression of Ca +2 Signaling Pathway and Lipoxygenase Gene Chandrama Prakash Upadhyaya & Mayank Anand Gururani & Ram Prasad & Ajit Verma Received: 20 December 2012 / Accepted: 7 April 2013 # Springer Science+Business Media New York 2013 Abstract Piriformospora indica is an axenically cultivable phytopromotional endo- symbiont that mimics capabilities of arbuscular mycorrhizal fungi. This is a basidio- mycete of the Sebacinaceae family, which promotes growth, development, and seed production in a variety of plant species. We report that the cell wall extract (CWE) from P. indica induces tuberization in vitro and promotes tuber growth and yield in potato. The CWE altered the calcium signaling pathway that regulates tuberization process. An increase in tuber number and size was correlated with increased transcript expression of the two Ca 2+ -dependant proteins (CaM1 and St-CDPK1) and the lipoxygenase (LOX) mRNA, which are known to play distinct roles in potato tuberization. External supplementation of Ca 2+ ions induced a similar set of tuberization pathway genes, indicating presence of an active Ca 2+ in the CWE of P. indica. Since potato tuberization is directly influenced by the presence of microflora in nature, the present study provides an insight into the novel mechanism of potato tuberization in relation to plant–microbe association. Ours is the first report on an in vitro tuber-inducing beneficial fungus. Keywords Calcium signaling pathway . Lipoxygenase . Piriformospora indica . Solanum tuberosum . Tuberization Appl Biochem Biotechnol DOI 10.1007/s12010-013-0231-1 C. P. Upadhyaya (*) Department of Botany, Guru Ghasidas Central University, Bilaspur 495009, India e-mail: cpupadhyay@gmail.com M. A. Gururani Subtropical Horticulture Research Institute, Faculty of Biotechnology, Jeju National University, Jeju 690756, South Korea R. Prasad : A. Verma Amity Institute of Microbial Technology, Amity University, Noida 201303, India