硫元素是植物生長發(fā)育必不可少的大量元素之一,。植物主要通過根從土壤中以硫酸根的形式獲取硫元素，并將其轉(zhuǎn)運(yùn)到植物的不同組織,，然后被組織細(xì)胞同化利用,，參與植物新陳代謝。植物所吸收獲得的硫酸根經(jīng)過硫同化途徑被還原為低價硫,，然后參與含硫化合物（如半胱氨酸,，甲硫氨酸等）的形成，而多余的硫酸根則被運(yùn)輸?shù)狡渌M織和（或）在細(xì)胞的葉泡內(nèi)儲存,。
中國科學(xué)院西雙版納植物園植物基因功能研究組余迪求研究員領(lǐng)銜的研究小組在microRNA調(diào)控擬南芥發(fā)育調(diào)節(jié)研究方面取得新進(jìn)展,，相關(guān)成果文章公布在The Plant Journal上。
研究組系統(tǒng)解釋了microRNA395如何參與調(diào)控硫酸根在擬南芥體內(nèi)的吸收,、轉(zhuǎn)運(yùn)和同化的生物學(xué)過程及其分子機(jī)制,。
在成熟葉衰老過程中，硫元素一般被認(rèn)為是不能向幼葉轉(zhuǎn)移的,。但是該研究發(fā)現(xiàn),，在硫充足的情況下，擬南芥的硫轉(zhuǎn)蛋白SULTR2;1可以將游離態(tài)形的硫酸根從老葉轉(zhuǎn)運(yùn)到正在發(fā)育的幼葉,。當(dāng)植物處于硫缺乏條件時,，植物的幼葉往往首先表現(xiàn)出缺硫癥狀（如黃化），這似乎說明硫酸根是不可以轉(zhuǎn)移的,。但進(jìn)一步的研究表明,，在缺硫情況下，植物體內(nèi)MicroRNA395的表達(dá)水平被顯著地誘導(dǎo)提高。受到誘導(dǎo)的microRNA395迅速而有效地抑制了其靶基因SULTR2;1的表達(dá),，從而限制了硫酸根從老葉向新葉的轉(zhuǎn)運(yùn),。
microRNA395不僅參與硫酸根的轉(zhuǎn)運(yùn)，而且還在硫酸根的同化途徑中起作用,。micorRNA395所調(diào)控的另外一組靶基因是APS酶,，它們在硫同化途徑中負(fù)責(zé)活化硫酸根。在缺硫條件下microRNA395通過抑制APS1和APS4,，部分限制了硫酸根進(jìn)入同化途徑,。通過高表達(dá)microRNA395基因，研究發(fā)現(xiàn)轉(zhuǎn)基因植物過量積累了硫酸根,，這說明microRNA395參與了硫酸根的積累,。
通過生物信息學(xué)預(yù)測發(fā)現(xiàn)，microRNA395在單子葉和雙子葉植物中非常保守,，并且其所調(diào)控的靶基因也是非常保守的。這表明microRNA395參與硫代謝調(diào)控的分子機(jī)制也適用于其他植物物種,。
該研究詳盡的闡述了microRNA395如何調(diào)控硫酸根在擬南芥葉片中的積累和轉(zhuǎn)運(yùn),，解釋了植物應(yīng)對缺硫情況的機(jī)制，為現(xiàn)代農(nóng)業(yè)耕作提供了一定的理論依據(jù),。(生物谷Bioon.com)
生物谷推薦原文出處：
The Plant Journal doi: 10.1111/j.1365-313X.2010.04216.x
MicroRNA395 mediates regulation of sulfate accumulation and allocation in Arabidopsis thaliana
Gang Liang a,b , Fengxi Yang a and Di-Qiu Yu a,*
a Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming, Yunnan 650223, PR China
b Graduate University of Chinese Academy of Sciences, Beijing 100049, PR China
Sulfur is a macronutrient necessary for plant growth and development. Sulfate, a major source of sulfur, is taken up by plant roots and transported into different tissues for assimilation. During sulfate limitation, expression of miR395 is significantly up-regulated. miR395 targets two families of genes, ATP Sulfurylases (APS) and Sulfate Transporter2;1 (SULTR2;1, also called AST68), both of which are involved in the sulfate metabolism pathway. Their transcripts are suppressed strongly in miR395-overexpressing transgenic Arabidopsis, which over-accumulates sulfate in the shoot, but not in the root. APS1 knock-down mutants accumulate two-fold more sulfate compared with the wild-type. By constructing APS4-RNAi transgenic plants, we found that silencing the APS4 gene also results in over-accumulation of sulfate. Even though miR395-overexpressing transgenic plants over-accumulate sulfate in the shoot, they display sulfur deficiency symptoms. Additionally, the distribution of sulfate from old to younger leaves is impaired in miR395-overexpressing plants, which is similar to a SULTR2;1 loss-of-function mutant. The aps1-1sultr2;1APS4RNAi triple repressed mutants phenocopied miR395-overexpressing plants. Our research revealed that miR395 is involved in the regulation of sulfate accumulation and allocation by targeting APSs and SULTR2;1, respectively.
