Rhizomes are modified stems that grow horizontally underground in various perennial species, a growth habit that is advantageous for vigorous asexual proliferation. In Oryza longistaminata, a rhizomatous wild relative of cultivated rice (Oryza sativa), leaves in the aerial shoots consist of a distal leaf blade and a proximal leaf sheath [1]. Leaf blade formation is, however, suppressed in rhizome leaves. In O. sativa, BLADE-ON-PETIOLE (BOP) genes are the main regulators of proximal-distal leaf patterning [2]. During the juvenile phase of O. sativa, BOP expression is maintained at high levels by the small regulatory RNA microRNA156 (miR156), leading to formation of leaves consisting predominantly of the sheath. Here, we show that in O. longistaminata, high expression of BOPs caused by miR156 was responsible for suppression of the blade in rhizomes and that bop loss-of-function mutants produced leaves consisting of the leaf blade only. Rhizome growth in soil was also hampered in the mutants due to a severe reduction in rhizome tip stiffness. Leaf blade formation is also suppressed in the stolons of Zoysia matrella, a monocot species, and in the rhizomes of Houttuynia cordata, a dicot species, indicating that leaf blade suppression is widely conserved. We also show that strong expression of BOP homologs in both rhizome and stolon leaves rather than in aerial leaves is another conserved feature. We propose that suppression of the leaf blade by BOP is an evolutionary strategy that has been commonly recruited by both rhizomatous and stoloniferous species to establish their unique growth habit.

中文翻译：

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叶片上直立同源物抑制叶片发育是地下根茎生长的常见策略。

根茎是经过修饰的茎，可以在各种多年生物种的地下水平生长，这种生长习性有利于剧烈的无性繁殖。在长米野生稻（Oryza sativa）的近缘野生稻中，空中芽中的叶子由远端叶片和近端叶鞘组成[1]。然而，在根状茎叶中抑制了叶片的形成。在O. sativa中，叶片上的blade（BOP）基因是近端-远端叶片模式的主要调节因子[2]。在O. sativa的幼年期，BOP表达通过小的调节性RNA microRNA156（miR156）维持在高水平，导致形成主要由鞘组成的叶片。在这里，我们证明了在O. longistaminata中 由miR156引起的BOP的高表达导致根茎中叶片的抑制，并且bop功能丧失的突变体产生的叶片仅由叶片组成。由于根茎尖端硬度的严重降低，突变体中土壤的根茎生长也受到阻碍。在单子叶植物结缕草的the茎和双子叶植物鱼腥草的根茎中，也抑制了叶片的形成，这表明广泛抑制了叶片的抑制。我们还表明，在根茎和茎叶而不是气生叶中，BOP同源物的强表达是另一个保守的特征。我们提出，用BOP抑制叶片是一种进化策略，根茎和lon茎物种通常都采用这种策略来建立其独特的生长习性。