LONGIFOLIA1andLONGIFOLIA2, two homologous genes,regulate longitudinal cell elongation inArabidopsis

Abstract

Plants have diversified their leaf morphologies to adapt to diverse ecological niches. The molecular components responsible for regulating leaf morphology, however, have not been fully elucidated. By screening Arabidopsis activation-tagging lines, we identified a dominant mutant, which we designated longifolia1-1D (lng1-1D). lng1-1D plants were characterized by long petioles, narrow but extremely long leaf blades with serrated margins, elongated floral organs, and elongated siliques. The elongated leaves of the mutant were due to increased polar cell elongation rather than increased cell proliferation. Molecular characterization revealed that this phenotype was caused by overexpression of the novel gene LNG1, which was found to have a homolog, LNG2, in Arabidopsis. To further examine the role of the LNG genes, we characterized lng1 and lng2 loss-of-function mutant lines. In contrast to the elongated leaves of lng1-1D plants, the lng1 and lng2 mutants showed slightly decreased leaf length. Furthermore, the lng1-3 lng2-1 double mutant showed further decreased leaf length associated with less longitudinal polar cell elongation. The leaf widths in lng1-3 lng2-1 mutant plants were similar to those in wild type, implying that the role of LNG1 and LNG2 on polar cell elongation is similar to that of ROTUNDIFOLIA3 (ROT3). However, analysis of a lng1-3 lng2-1 rot3-1 triple mutant and of a lng1-1D rot3-1 double mutant indicated that LNG1 and LNG2 promote longitudinal cell elongation independently of ROT3. Taken together, these findings indicate that LNG1 and LNG2 are new components that regulate leaf morphology by positively promoting longitudinal polar cell elongation independently of ROT3 in Arabidopsis.

Natural Variations in SLG7 Regulate Grain Shape in Rice

“…Morphological and cellular analyses indicated that SLG7 has a function in regulating cell elongation in spikelets ( Figure 5). Similar to our data, LNG1 and LNG2 were also reported to play a positive role in increasing leaf and silique length through longitudinal cell elongation in Arabidopsis ( Lee et al 2006). These results suggested that the functions of SLG7 family members are probably conserved across monocots and dicots.…”

“…The BLASTP analysis revealed that SLG7 shares numerous putative homologs (Figure 3), including two functionally characterized genes, LNG1 (At5g15580) and LNG2 (At3g02170), both of which function in the elongation of leaves, siliques, and seeds in Arabidopsis (Lee et al 2006). LNG2 (also named TON1 Recruiting Motif 1) is identified as a microtubule-associated protein, which is able to target TON1 to cortical microtubules (Drevensek et al 2012).…”

“…Arabidopsis has four homologs of SLG7, but only two of them, LONGIFOLIA1 (LNG1, At5g15580) and LONGIFOLIA12 (LNG2, At3g02170), were functionally characterized. Both of them activate longitudinal organ expansion (Lee et al 2006). …”

Genetic Dissection of Leaf Development in Brassica rapa Using a Genetical Genomics Approach

“…2 and 5B; Table III). LNG1 mutants affect leaf polar cell elongation in Arabidopsis (Lee et al, 2006). The previously characterized leaf-adaxialized kan1, kan2 double mutant produces finger-shaped protrusions on the abaxial surface (Pekker et al, 2005).…”

The IQD Family of Calmodulin-Binding Proteins Links Calcium Signaling to Microtubules, Membrane Subdomains, and the Nucleus

“…Helical growth aberrations and altered leaf shape were reported for tomato sun lines (Wu et al, 2011) and often are associated with defects in MT functions (Buschmann et al, 2004;Ishida et al, 2007). Moreover, the growth defects are reminiscent of plants overexpressing LONGIFOLIA1/TON1 RECRUITING MOTIF2 (TRM2), which encodes a plant-specific MAP (Lee et al, 2006;Drevensek et al, 2012). Hence, the observed phenotypes point to roles of IQD16 in the regulation of MT arrays.…”