Plant Molecular Biology 35: 433–442, 1997. 433 c 1997 Kluwer Academic Publishers. Printed in Belgium. Two growth-related organ-specific cDNAs from Cicer arietinum epicotyls Francisco J. Mu˜ noz, Berta Dopico and Emilia Labrador Departamento de Biolog´ ia Vegetal (Fisiolog´ ia Vegetal), Universidad de Salamanca, Avda. Campo Charro S/n, 37008 Salamanca, Spain ( author for correspondence) Received 19 December 1996; accepted in revised form 23 May 1997 Key words: chickpea, epicotyls, growth, tissue-specific gene expression Abstract Two cDNAs, CanST-1 and CanST-2, encoding two different growth-related organ-specific sequences have been isolated from a cDNA library from growing epicotyls of Cicer arietinum. An intriguing property of these two clones is the presence in their coding region of a repeated sequence which is highly conserved except for the number of repeats. The corresponding genes of CanST-1 and CanST-2 encode for proteins related to elongation processes. CanST-1 and CanST-2 are up-regulated during epicotyl growth, the transcript levels of both clones decrease when the growth of epicotyls is inhibited by several treatments and their expression increases when epicotyls resume growth. Furthermore, clones CanST-1 and CanST-2 are tissue-specific and are only expressed in epicotyls, mesocotyls, roots and stem tissues whose cells undergo elongation processes. Neither clone was found to be expressed in other organs such as cotyledons, leaves, flowers, pods and immature seeds. The results of auxin (IAA) and brassinolides (BR) treatments suggest that the processes in which the proteins encoded by CanST-1 and CanST-2 are involved are not mediated by these hormones. Introduction Plant cell growth is a highly complex process funda- mental to plant development that requires the products of many genes taking part in numerous life processes. These genes will be activated or repressed as a function of cellular needs at any given moment with a temporal and spatial regulation. The mechanisms of the regu- lation of genes involved in growth are not clear and many aspects remain to be elucidated. Throughout plant growth, the differential expres- sion of a number of genes occurs. The products of these genes may participate in specific processes that guarantee the correct plant development. In the same way, factors that modify growth either positively or negatively, also affect the expression of different genes. In this sense, some growth regulation substances such as IAA [1, 15], giberellins [10] or brassinolides (BR) The nucleotide sequence data reported will appear in the EMBL, GenBank and DDBJ Nucleotide Sequence Databases under the accession numbers X97454 (CanST-1) and X97455 (CanST-2). [19] induce the expression of a whole array of specific genes. To understand plant cell growth, it is necessary to isolate and characterisize the genes that are specific to growing tissues as well as to study genes specific to certain developmental stages. In the former case, the idea is to identify genes that are expressed only or mostly during active phases of growth and that show little or no expression in tissues with low or no growth. In the present work our aim was to isolate growth- related clones from a cDNA library from Cicer arietin- um epicotyls in the active phase of elongation (5 days) and to characterize them. The differential expression of the genes corresponding to these clones in differ- ent developmental stages, different organs and under different growth conditions could afford an idea of the possible function played by the corresponding proteins along the complex process of growth.