MicroRNA534a control of BLADE-ON-PETIOLE 1 and 2 mediates juvenile-to-adult gametophyte transition in Physcomitrella patens.
MicroRNA534a control of BLADE-ON-PETIOLE 1 and 2 mediates juvenile-to-adult gametophyte transition in Physcomitrella patens.
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MicroRNA534a 控制 BLADE-ON-PETIOLE 1 和 2 介导小立碗藓幼年到成年配子体的转变。
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
T. Arazi
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作者：
O. Saleh;Noa Issman;Gotelinde I. Seumel;R. Stav;A. Samach;R. Reski;W. Frank;T. Arazi
拟南芥叶片-叶柄基因编码一对转录共激活因子，通过促进其近端区域的细胞分化来调节侧向器官结构。为了深入了解BOP基因在陆地植物进化早期的作用，我们表征了小立碗藓BOP 1和BOP 2及其负调控因子Pp-miR 534 a的功能。我们发现，在缺乏成熟Pp-miR 534 a的Δ PpMIR 534 a突变体中，PpBOP 1/2的切割被消除，导致PpBOP 1/2转录水平升高。这些功能丧失的突变体显示出加速的配子体发育，从而使PpBOP 1/2水平升高与过早的芽形成相关。这进一步得到了我们的发现的支持，即暴露于细胞分裂素，这是已知的诱导芽形成的茎丝，下调PpMIR 534 a转录，并增加积累的PpBOP 1在顶端茎丝细胞。报告基因融合表明，PpMIR 534 a是普遍表达的原丝体，而PpBOP 1/2的积累几乎只限于有效的茎丝顶端细胞和他们的侧分支的初始，但没有分化的细胞。总之，我们的数据表明，PpBOP 1/2作为正调节原丝体分化和Pp-miR 534 a是必要的，以控制时间的幼年到成年配子体过渡空间限制其表达茎丝干细胞。随着原丝体的发育，细胞分裂素水平的增加下调了这些细胞中Pp-MIR 534 a的转录，直到达到触发细胞分化和芽形成的PpBOP 1/2的阈值水平。
The Arabidopsis thaliana BLADE-ON-PETIOLE genes encode a pair of transcriptional coactivators that regulate lateral organ architecture by promoting cell differentiation in their proximal regions. To gain insight into the roles of BOP genes early in land plant evolution, we characterized the functions of Physcomitrella patens BOP1 and BOP2 and their negative regulator Pp-miR534a. We show that in ΔPpMIR534a mutants lacking mature Pp-miR534a, cleavage of PpBOP1/2 is abolished, leading to elevated PpBOP1/2 transcript levels. These loss-of-function mutants display an accelerated gametophore development thus correlating elevated levels of PpBOP1/2 with premature bud formation. This is further supported by our finding that exposure to cytokinin, which is known to induce bud formation on caulonema, downregulates PpMIR534a transcription and increases the accumulation of PpBOP1 in apical caulonema cells. Reporter gene fusions showed that PpMIR534a is ubiquitously expressed in protonema whereas PpBOP1/2 accumulation is restricted almost exclusively to potent caulonema apical cells and their side branch initials, but absent from differentiated cells. Together, our data propose that PpBOP1/2 act as positive regulators of protonema differentiation and that Pp-miR534a is required to control the timing of the juvenile-to-adult gametophyte transition by spatially restricting their expression to caulonema stem cells. As protonemata develop, increased cytokinin levels downregulate Pp-MIR534a transcription in these cells until a threshold level of PpBOP1/2 is reached that triggers cell differentiation and bud formation.