Sym28, a gene controlling stem architecture and nodule number, is localized on linkage group V

Abstract

Garden pea (Pisum sativum L.) represents one of the most important models for studying plant developmental genetics. This species serves as a model object for most investigations on the genetic control of formation of compound inflorescence, compound leaf and of symbiotic interaction with nitrogen-fixing bacteria (nodulation). The latter phenomenon is typical for most legumes and is of significant theoretical and practical interest. By now, multiple genes involved in the genetic control of nodulation have been identified (for review see (2)). One of the key processes in plant development is the regulation of stem apical meristem (SAM) activity. Studies on the model plant Arabidopsis thaliana (L.) Heynh. (Brassicaceae) demonstrated that equilibrium between SAM proliferation and keeping its volume stable is reached via the CLAVATA-WUSCHEL regulatory feedback loop. Expression of the gene WUSCHEL (WUS) maintains the meristematic condition of cells and activates expression of the CLAVATA (CLVI, CLV2 and CLV3) gene family. CLV proteins negatively regulate expression of WUS thus limiting its expression pool (14). Mutations in CLV genes lead to abnormal enlargement of the WUS-expressing zone resulting in flower and stem fasciation. Genes of the FASCIATA (FAS! and FAS2) family also serve as negative regulators of WUS (5).