Nitrogen deprivation stimulates symbiotic gland development in Gunnera manicata
Nitrogen deprivation stimulates symbiotic gland development in Gunnera manicata
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DOI：
10.1104/pp.105.064931
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发表时间：
2005-09-01
期刊：
影响因子：
7.4
通讯作者：
Elhai, J
中科院分区：
文献类型：
--
作者：
Chiu, WL;Peters, GA;Elhai, J
古内拉属是被子植物中唯一一个能在胞内寄生蓝藻的属，也是陆地植物中唯一一个能在胞内寄生蓝藻的属。蓝细菌的运动细丝，称为藻殖体，通过植物特化的茎腺细胞在贡内拉植物中定居。一般认为，古那拉属植物都具有功能性腺体，以利于共生。然而，我们发现，当Gunnera manicata植物生长在氮（N）充足的培养基上时，茎腺发育并不发生，而是在植物被剥夺结合N时在预定位置启动。氮素营养是腺体发育的主要决定因素，外源碳源（蔗糖）加速了腺体发育。此外，高水平的蔗糖刺激形成的胼胝体样组织的地方，在N-充满条件下的腺体。植物生长素运输抑制剂1-naphthylphthalamic酸处理防止腺体发育N限制培养基，最有可能是通过防止资源重新分配从叶到茎。优化的条件下，发现在体外建立的念珠藻-Gunnera共生体的成熟腺体与藻殖体从念珠藻punctiforme，蓝藻菌株的全基因组序列是可用的。与未接种的植株相比，G. Manicata植物被N. punctiforme在N限制培养基上能继续生长。了解Gunnera植物的不寻常的适应N-有限的环境的性质，可能会揭示植物蓝藻共生的进化，并可能建议一条路线，以建立固氮蓝藻和作物之间的生产协会。
Gunnera is the only genus of angiosperms known to host cyanobacteria and the only group of land plants that hosts cyanobacteria intracellularly. Motile filaments of cyanobacteria, known as hormogonia, colonize Gunnera plants through cells in the plant's specialized stem glands. It is commonly held that Gunnera plants always possess functional glands for symbiosis. We found, however, that stem gland development did not occur when Gunnera manicata plants were grown on nitrogen (N)-replete medium but, rather, was initiated at predetermined positions when plants were deprived of combined N. While N status was the main determinant for gland development, an exogenous carbon source ( sucrose) accelerated the process. Furthermore, a high level of sucrose stimulated the formation of callus-like tissue in place of the gland under N-replete conditions. Treatment of plants with the auxin transport inhibitor 1-naphthylphthalamic acid prevented gland development on N-limited medium, most likely by preventing resource reallocation from leaves to the stem. Optimized conditions were found for in vitro establishment of the Nostoc-Gunnera symbiosis by inoculating mature glands with hormogonia from Nostoc punctiforme, a cyanobacterium strain for which the full genome sequence is available. In contrast to uninoculated plants, G. manicata plants colonized by N. punctiforme were able to continue their growth on N-limited medium. Understanding the nature of the Gunnera plant's unusual adaptation to an N-limited environment may shed light on the evolution of plant-cyanobacterium symbioses and may suggest a route to establish productive associations between N-fixing cyanobacteria and crop plants.