Regulation of LANCEOLATE by miR319 is required for compound-leaf development in tomato

Abstract

Plant leaves show pronounced plasticity of size and form. In the classical, partially dominant mutation Lanceolate (La), the large compound leaves of tomato (Solanum lycopersicum) are converted into small simple ones. We show that LA encodes a transcription factor from the TCP family containing an miR319-binding site. Five independent La isolates are gain-of-function alleles that result from point mutations within the miR319-binding site and confer partial resistance of the La transcripts to microRNA (miRNA)-directed inhibition. The reduced sensitivity to miRNA regulation leads to elevated LA expression in very young La leaf primordia and to precocious differentiation of leaf margins. In contrast, downregulation of several LA-like genes using ectopic expression of miR319 resulted in larger leaflets and continuous growth of leaf margins. Our results imply that regulation of LA by miR319 defines a flexible window of morphogenetic competence along the developing leaf margin that is required for leaf elaboration.

MicroRNAs in tomato plants

“…Itaya et al identified 6 putative miRNAs whose target genes are unknown, and also found that SlsmR-596 (23 nt) contains the sequence of the putative miRNA2 (18 nt) reported previously [26]. However, these authors did not recover miR319 reported by Ori et al [19]. Most important of all, they established a database for tomato sRNAs (http://ted.bti.cornell.edu/cgi-bin/TFGD/ sRNA/home.cgi) that is updated regularly and which can provide ultramodern and overall knowledge.…”

“…Ori et al [19] found that the reduced sensitivity to miR319 resulted in elevated LA expression in very young leaf primordia and accelerated differentiation of leaf margins. On the other hand, increased expression of miR319 led to larger leaflets and continuous growth of leaf margins.…”

“…Although the tomato genome database is not complete, great progress has been made in tomato miRNA research recently [19][20][21]. In this review, we summarize our current knowledge and advance future directions for microRNA research in tomato.…”

“…In addition, mature miRNAs and the precursors of miR319, miR171 and miR162 have been cloned [15,19,26].…”

Fine tuning of auxin signaling by miRNAs

“…They are involved in regulating the various aspects of shoot morphogenesis from meristem establishment and maintenance (Juarez et al, 2004, McHale and Koning, 2004, Mallory et al, 2004aJuarez et al, 2004;Zhong and Ye, 2004;Bowman, 2004;Bao et al, 2004;Kim et al, 2005) to leaf development including abaxial-adaxial polarity (Palatnik et al, 2003), organ boundaries (Laufs et al, 2004), shape and complexity (Ori et al, 2007).…”