Fatty acids (FAs) are major components for cell or organelle membrane lipids, and precursors of other significant complex molecules including waxes and cutin. Apart from studies in Arabidopsis and rice the functions of KASI in controlling FAs biosynthesis and regulating growth and development have not been characterized in other plants.

   Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to understand the functions of 3-ketoacyl-acyl-carrier protein synthase I (KASI) in tobacco (Nicotiana tabacum), an alternative biofuel plant in recent years. They isolated two NtKASI orthologs from Nicotiana tabacum that were highly conserved among various plants and investigated whether the two genes had functional reduandancy

. They found that KASIgenes, particular for NtKASI-1 gene, were highly transcribed in floral organ compared with vegetative tissues, implying their important function in reproductive stage. The knock-down NtKASI-1 (kasI-1 RNAi lines) plants exhibited the variegated leaves and semi-dwarf phenotype. NtKASI-1 gene can boost tobacco growth and NtKASI genes significantly influenced the tobacco seed weight as well as lipid content, particularly for NtKASI-1 gene.

  The researchers also evaluated the specific roles of NtKASI-1 and NtKASI-2 in triacylglycerols (TAG) biosynthesis in tobacco seeds. The results showed that the over-expressed NtKASI-1 significantly enhanced oil content and seed weight, but the silenced NtKAkasI-1/2 RNAi genes significantly decreased the oil content and seed weights, clearly suggesting that NtKASI-1 might play a critical role in regulating TAG accumulation in tobacco seeds. In addition, they noted that the silenced NtKASI-1 (kasI-1 RNAi lines) did not exhibit a significant reduction in the oil content and seed weight.

  They revealed that the NtKASI genes, particularly NtKASI-1, are crucial for regulating fatty acids synthesis in leaf and seeds, and play a key role in tobacco vegetative and reproductive growth. There was a partial functional redundancy between NtKASI-1 and NtKASI-2, and particularly NtKASI-1 had a stronger role in regulating growth and development in tobacco.

  The study entitled “β-Ketoacyl-acyl Carrier Protein Synthase I (KASI) Plays Crucial Roles in the Plant Growth and Fatty Acids Synthesis in Tobacco” has been published in International Journal of Molecular Sciences.

Contact

LIU Aizhong

Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany

E-mail: liuaizhong@mail.kib.ac.cn