Different expression patterns of duplicated PHANTASTICA-like genes in Lotus japonicus suggest their divergent functions during compound leaf development

Abstract

Recent studies on leaf development demonstrate that the mechanism on the adaxial-abaxial polarity pattern formation could be well conserved among the far-related species, in which PHANTASTICA (PAHN)-like genes play important roles. In this study, we explored the conservation and diversity on functions of PHAN-like genes during the compound leaf development in Lotus japonicus, a papilionoid legume. Two PHAN-like genes in L. japonicus, LjPHANa and LjPHANb, were found to originate from a gene duplication event and displayed different expression patterns during compound leaf development. Two mutants, reduced leaflets1 (rel1) and reduced leaflets3 (rel3), which exhibited decreased adaxial identity of leaflets and reduced leaflet initiation, were identified and investigated. The expression patterns of both LjPHANs in rel mutants were altered and correlated with abnormalities of compound leaves. Our data suggest that LjPHANa and LjPHANb play important but divergent roles in regulating adaxial-abaxial polarity of compound leaves in L. japonicus.

Regulation of Compound Leaf Development by PHANTASTICA in Medicago truncatula

“…In Lotus japonicus, a tandem repeat of ARP genes, LjPHAN1 and LjPHAN2, has been reported (Luo et al, 2005). Amino acid sequence alignments of ARP genes from legume and nonlegume species revealed extensive amino acid sequence similarities in the NH 2 -terminal MYB domain and the COOH-terminal domain among the sequences (Supplemental Fig.…”

Control of Compound Leaf Development byFLORICAULA/LEAFYOrthologSINGLE LEAFLET1inMedicago truncatula

“…However, development of distal tendrils follows a basipetal pattern, giving rise to the unique compound leaf structure of pea plants (Hofer and Ellis, 1998). By contrast, the order of leaflet primordial development is basipetal in L. japonicus and other compound-leafed species (Hofer and Ellis, 1998;Gourlay et al, 2000;Luo et al, 2005). To facilitate characterization of leaf mutants in M. truncatula, we investigated leaf developmental processes with both visual and scanning electron microscopic (SEM) analyses.…”

STM/BP-Like KNOXI Is Uncoupled from ARP in the Regulation of Compound Leaf Development inMedicago truncatula

“…Their transcripts were detected at sites of leaf initiation (P0), but excluded from the SAM, forming a mutually exclusive pattern with KNOXI genes. To our surprise, M. truncatula PHAN has a distinct expression pattern, compared with those in Arabidopsis, C. hirsute, and other legume species (Byrne et al, 2000;Luo et al, 2005;Tattersall et al, 2005; (Supplemental Figure 13). M. truncatula PHAN is diffusely expressed throughout the SAM, showing an overlapping expression domain with KNOXI genes.…”

“…On the other hand, ARP expression domains are associated with the adaxial side of leaf primordia at early developmental stages in compound-leafed species. For example, PHAN displayed adaxial expression in the P3/P4 leaf primordia of tomato (Kim et al, 2003a(Kim et al, , 2003b, P1 of L. japonicus (Luo et al, 2005), and P3 of pea (Tattersall et al, 2005) (Supplemental Figure 13). In M. truncatula, PHAN transcripts were detected in both the adaxial and abaxial sides of leaf primordia from P1 to P5.…”

“…To start with, we focused on KNOX1, KNOX2, and KNOX6 because the conserved regulatory module was reported mainly between STM/BP-like KNOXI genes and ARP (Kim et al, 2003b;Luo et al, 2005;Tattersall et al, 2005;. Previous studies showed that ectopic expression of KNOXI genes in compound-leafed species results in a dramatic increase in leaf complexity through promoting CK biosynthesis (Hareven et al, 1996;Jasinski et al, 2005;Yanai et al, 2005;Champagne et al, 2007).…”