Involvement of a tobacco leucine-rich repeat-extensin in cell morphogenesis

Abstract

The unique mutant nolac-K4 (non-organogenic callus with loosely attached cells), which was generated by T-DNA transformation using leaf-disk cultures of haploid Nicotiana plumbaginifolia, has lost the ability to form adventitious shoots and also shows decreased intercellular attachment. The gene tagged with the T-DNA in this line, named NpLRX1 (LRR-EXTENSIN 1), is a novel tobacco gene that encodes a cell-wall protein containing chimeric leucine-rich repeat and extensin domains. The gene is highly similar to the Arabidopsis LRX genes, and phylogenetic analysis places it in the vegetative LRX clade. NpLRX1 is expressed ubiquitously in vegetative tissues, strongly in the leaf and root vascular bundles, and in emerging lateral roots and root tips. Tobacco leaf disks transformed with an NpLRX1-RNAi construct displayed aberrant adventitious buds and disorganized cell morphogenesis with large intercellular spaces. The shapes of NpLRX1-RNAi-transformed BY-2 cells were irregular, and the cells showed disorganized cortical microtubules. These results suggest that NpLRX1, the lack of which may be responsible for the nolac-K4 mutation, is a new tobacco LRX gene that has regulatory roles in cell morphogenesis that are essential for plant tissue development.