Rice NARROW LEAF1 Regulates Leaf and Adventitious Root Development

Abstract

To improve our understanding of the molecular-genetic mechanisms governing leaf and root development in rice (Oryza sativa), we investigated narrow leaf1 (nal1), a pleiotropic mutant with short and narrow leaves, semi-dwarf stature, and fewer adventitious (or crown) roots. The narrow leaf5 (nal5) and nal1 mutants display similar defects in leaf and root development. Sequence analysis and complementation tests showed that nal5 is allelic to nal1. NAL1 encodes a putative trypsin-like serine/cysteine protease; the coding region of nal5 contains a missense mutation and nal1 harbors a 30-bp deletion. Quantitative real-time PCR revealed that nal1 mutants have altered expression levels of many OSHB, YABBY, and PIN-FORMED genes associated with leaf development and auxin transport. In addition, expression levels of CROWN ROOTLESS genes are markedly down-regulated in nal1. These results indicate that NAL1 functions in the regulation of both leaf and adventitious root development at the transcriptional level. Notably, exogenous auxin treatment rescued the reduced number of adventitious roots in nal1. Based on our results, we propose that NAL1 plays important roles in adventitious root development in rice.