Characterization of leaf shape-related novel LONGIFOLIA gene and development of an efficient transformation system in plant

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 of Arabidopsis activation tagging lines, I identified a dominant mutant that I designated longifolial -ID (ingl-1D). The ingl-ID 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, LNG], which was found to have a homolog, LNG2, in Arabidopsis. To further examine the role of LNG] and LNG2, I characterized ingl and lng2 loss-offunction mutant lines. In contrast to the elongated leaves of ingl-ID plants, the ingl and lng2 mutants showed slightly decreased leaf length. Furthermore, the ingl lng2 double mutant showed further decreased leaf length associated with less longitudinal polar cell elongation. The leaf widths in ingl lng2 mutant plants were similar to those in wild type, implying that the role of LNGI and LNG2 on polar cell elongation is similar to that of ROT3. However, analysis of a ingl ing2 rot3 triple mutant and a ingl-ID rot3 double mutant indicated that LNG1 and LNG2 promote polar cell elongation independent of ROT3. Taken together, these findings indicate that LNGI and LNG2 are new components that regulate leaf morphology by positively promoting longitudinal polar cell elongation independent of ROT3 in Arabidopsis. Using cotyledonary explants excised from seedlings germinated in vitro, efficient plant regeneration via organogenesis was established for two winter squash (Cucurbita maxima Duch.) cultivars. To establish optimal conditions for adventitious shoot induction, a variety of explants were prepared from seedlings of ...