Multicellular genesis of leaf primordium was demonstrated via chimaeric transgenic plant of maize (Zea mays L.) regenerated from Type II calli
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Type-II embryonic calli were induced from immature embryos of maize (Zea mays L.) genotype YD and bombarded with beta-glucuronidase gene. Bombarded calli were proliferated on normal N6 medium for 2 weeks at 26°C in the dark and selected on N6 medium containing 1 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) and 5 mg/l phosphinothricin (PPT) but without casamino acids and proline under the same conditions for 14 days. Regeneration was carried out on hormone-free MS medium containing 5 mg/l phosphinothricin at 26°C under 3000 lux illumination. Plants over 8 cm were transplanted into soil and sprayed with 250 mg/l phosphinothricin when two new leaves appeared. Except normal transgenic plants, chimaeric transgenics also were regenerated in the present work. The expression pattern of beta-glucuronidase gene in leaves of chimaeric transgenic plant revealed that more than one cell formed leaf primordium at the initial stage, and filial cells stemed from each cell in leaf primordium arranged in a row longitudinally from leaf base to leaf apex. There was a clear boundary as a straight line between the area formed by transformed cells and the area formed by normal cells. A hypothesis was put forward that the primitive cells in leaf primordium divided in a longitudinal style, resulted in leaf elongation, then the filial cells divided transversally and synchronously toward the outside to broaden the leaf.
KeywordsChimaeric transgenic plant Beta-glucuronidase gene Leaf primordium of maize Multicellular genesis Type-II embryonic calli
This work was supported by National Natural Science Foundation of China (Grant number 30870194), Natural Science Foundation of Shaanxi Province (Grant number 2006C103), Research Project of Educational Department of Shaanxi Province (Grant number 08JK466) and Research Project of Provincial Key Laboratory of Shaanxi (Grant number 08JZ70).
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