文部省 科学研究費補助金 新学術領域研究 植物発生ロジックの多元的開拓

PubMed ID 25246492 Pubmed 日付 2014/Nov/
タイトル The conflict between cell proliferation and expansion primarily affects stem organogenesis in Arabidopsis.
ジャーナル Plant & cell physiology  2014/Nov/  55(11)  1994-2007 
著者 Maeda Saori S,Gunji Shizuka S,Hanai Kenya K,Hirano Tomonari T,Kazama Yusuke Y,Ohbayashi Iwai I,Abe Tomoko T,Sawa Shinichiro S,Tsukaya Hirokazu H,Ferjani Ali A
抄録 Plant shoot organs such as stems, leaves and flowers are derived from specialized groups of stem cells organized at the shoot apical meristem (SAM). Organogenesis involves two major processes, namely cell proliferation and differentiation, whereby the former contributes to increasing the cell number and the latter involves substantial increases in cell volume through cell expansion. Co-ordination between the above processes in time and space is essential for proper organogenesis. To identify regulatory factors involved in proper organogenesis, heavy-ion beam-irradiated de-etiolated (det) 3-1 seeds have been used to identify striking phenotypes in the A#26-2; det3-1 mutant. In addition to the stunted plant stature mimicking det3-1, the A#26-2; det3-1 mutant exhibited stem thickening, increased floral organ number and a fruit shape reminiscent of clavata (clv) mutants. DNA sequencing analysis demonstrated that A#26-2; det3-1 harbors a mutation in the CLV3 gene. Importantly, A#26-2; det3-1 displayed cracks that randomly occurred on the main stem with a frequency of approximately 50%. Furthermore, the double mutants clv3-8 det3-1, clv1-4 det3-1 and clv2-1 det3-1 consistently showed stem cracks with frequencies of approximately 97, 38 and 35%, respectively. Cross-sections of stems further revealed an increase in vascular bundle number, cell number and size in the pith of clv3-8 det3-1 compared with det3-1. These findings suggest that the stem inner volume increase due to clv mutations exerts an outward mechanical stress; that in a det3-1 background (defective in cell expansion) resulted in cracking of the outermost layer of epidermal cells.

 Flowering stem growth control

東京学芸大学自然科学系生命科学分野 Ferjani Ali研究室 Ali Ferjani  投稿日時[2015-02-10 09:51:08]

Plant organogenesis is regulated through robust control of constituent cell number and size. Past studies have examined organ size regulation in shoot structures, such as leaves and flowers, but not in flowering stems. In the paper of Maeda et al. (Plant & cell physiology 2014/Nov/ 55 (11):1994-2007) we clearly show that in the cell proliferation- and cell expansion-defective Arabidopsis double mutants「clv3-8 det3-1, clv2-1 det3-1, and clv1-4 det3-1」 flowering stems often exhibit severe cracking resulting in exposure of their inner tissues. These observations suggest that internal cell proliferation in stems exerts an outward mechanical stress that must be accompanied by appropriate levels of cell expansion in the epidermis to avoid cracking. A scanning electron microscopy image of clv3-8 det3-1 double mutant cracked stem was featured for the cover design of the PCP November issue. A more exciting work is now ongoing to further dissect the molecular mechanism behind flowering stem cracking.