SWEET11 and 15 as key players in seed filling in rice
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Jungil Yang, Dangping Luo, Bing Yang, Wolf B. Frommer, Joon‐Seob Eom
New Phytologist, 2018, 218(2): 604-615 DOI: 10.1111/nph.15004; 追溯原文......本站官方QQ群：62473826
apoplasmic pathway; caryopsis; endosperm; rice; sucrose transporter; SWEET
1 Institute for Molecular Physiology, Heinrich-Heine University Duesseldorf, 40225 Duesseldorf, Germany;
2 Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany;
3 Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA;
4 Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA 50011, USA;
5 Institute of Transformative Bio-Molecules (ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, JapanDespite the relevance of seed‐filling mechanisms for crop yield, we still have only a rudimentary understanding of the transport processes that supply the caryopsis with sugars. We hypothesized that SWEET sucrose transporters may play important roles in nutrient import pathways in the rice caryopsis.
We used a combination of mRNA quantification, histochemical analyses, translational promoter–reporter fusions and analysis of knockout mutants created by genomic editing to evaluate the contribution of SWEET transporters to seed filling.
In rice caryopses, SWEET11 and 15 had the highest mRNA levels and proteins localized to four key sites: all regions of the nucellus at early stages; the nucellar projection close to the dorsal vein; the nucellar epidermis that surrounds the endosperm; and the aleurone. ossweet11;15 double knockout lines accumulated starch in the pericarp, whereas caryopses did not contain a functional endosperm.
Jointly, SWEET11 and 15 show all the hallmarks of being necessary for seed filling with sucrose efflux functions at the nucellar projection and a role in transfer across the nucellar epidermis/aleurone interface, delineating two major steps for apoplasmic seed filling, observations that are discussed in relation to observations made in rice and barley regarding the relative prevalence of these two potential import routes.
SWEET11和15蔗糖轉(zhuǎn)運(yùn)蛋白調(diào)控水稻籽粒灌漿
盡管籽粒灌漿機(jī)制對(duì)作物產(chǎn)量具有相關(guān)性，但我們對(duì)于穎果的糖供應(yīng)轉(zhuǎn)運(yùn)進(jìn)程還只是個(gè)初步的了解。我們推測(cè)蔗糖轉(zhuǎn)運(yùn)蛋白SWEET可能在水稻穎果的營(yíng)養(yǎng)供給路徑中扮演重要的作用。我們通過(guò)綜合利用mRNA定量、組織化學(xué)分析和轉(zhuǎn)啟動(dòng)子-報(bào)道基因融合蛋白及利用基因組編輯敲除目標(biāo)基因獲得突變體等方法評(píng)估SWEET轉(zhuǎn)運(yùn)蛋白對(duì)于灌漿的貢獻(xiàn)。在水稻的穎果中，SWEET11和SWEET15基因具有最高的mRNA水平，其蛋白定位于4個(gè)關(guān)鍵位置，分別是：早期遍布珠心；靠近背面葉脈的珠心突起部分；環(huán)繞胚乳的珠心表皮；以及糊粉層。雙突變體ossweet11;15株系會(huì)在果皮中積累淀粉，而穎果中未形成具有功能的胚乳。另外，SWEET11和SWEET15蛋白對(duì)于灌漿期中在珠心突起的蔗糖流功能是必需的，這兩個(gè)蛋白還在珠心表皮和糊粉層的交界處祈禱轉(zhuǎn)運(yùn)作用，這兩步恰是質(zhì)外體種子填充的主要步驟。我們還討論了關(guān)于水稻和大麥關(guān)于這兩個(gè)潛在的運(yùn)輸渠道的相對(duì)優(yōu)勢(shì)。
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基因列表◄
白葉枯病抗性基因; 蔗糖轉(zhuǎn)運(yùn)蛋白; 結(jié)瘤素基因; 白葉枯病易感基因 xa13; Os-8N3; OsSWEET11 蔗糖轉(zhuǎn)運(yùn)蛋白; 白葉枯病易感基因 OsSWEET15