OsIAA29的定位表达表明生长素在调节早稻籽粒背糊粉层发育中起关键作用
水稻和其它谷类的胚乳在籽粒发育早期积累高浓度的植物生长素-吲哚-3-乙酸(IAA)。然而，IAA在胚乳发育过程中的信号传导和功能尚不清楚。
在此，我们报道了OsYUC12（一个生长素生物合成基因）和OsIAA29（编码一个非典型AUX/IAA）都在籽粒中独家表达，在授粉后5-6天达到最大值。OsYUC12的表达定位于糊粉质、亚糊粉质和胚,而OsIAA29的表达仅局限于维管束正下方的背糊粉质中的一条狭长的条带。虽然水稻缺乏胚乳转移细胞（ETCs）,但这一区域富含糖转运蛋白,可能在质外体营养转移中发挥关键作用,这与其它谷物中的ETCs相似。
OsIAA29仅在禾本科植物中有直系同源物；在籽粒发育早期也有特异性表达。OsYUC12和OsIAA29与两个基因(AL1和OsPR602)在时间上共同表达，这两个基因先前与背糊粉或ETCs的发育相关。与ZmMRP-1同源的一簇MYB相关基因（命名为OsMRPLs）也同时上调，该基因调控玉米等的发育。
ZmMRP-1的小麦同系物也在ETCs中表达。尽管以前的研究表明其它谷物中不存在ZmMRP-1的正交基因，但我们的研究表明OsIAA29和OsMRPLs及其在其它禾本科植物中的同源基因是生长素调控的、保守的信号网络的一部分，参与了具有ETC样功能的细胞在谷物发育过程中的分化。
Endosperm of rice and other cereals accumulates high concentrations of the predominant in planta auxin, indole-3-acetic acid (IAA) during early grain development. However, IAA signalling and function during endosperm development are poorly understood. Here, we report that OsYUC12 (an auxin biosynthesis gene) and OsIAA29 (encoding a non-canonical AUX/IAA) are both expressed exclusively in grains, reaching a maximum 5 to 6 days after pollination. OsYUC12 expression is localized in the aleurone, sub-aleurone and embryo, whereas OsIAA29 expression is restricted to a narrow strip in the dorsal aleurone, directly under the vascular bundle. Although rice has been reported to lack endosperm transfer cells (ETCs), this region of the aleurone is enriched with sugar transporters and is likely to play a key role in apoplastic nutrient transfer, analogous to ETCs in other cereals. OsIAA29 has orthologues only in grass species; expression of which is also specific to early grain development. OsYUC12 and OsIAA29 are temporally co-expressed with two genes (AL1 and OsPR602) previously linked to the development of dorsal aleurone or ETCs. Also up regulated at the same time are a cluster of MYB-related genes (designated OsMRPLs) homologous to ZmMRP-1, which regulates maize ETC development. Wheat homologues of ZmMRP-1 are also expressed in ETCs. Although previous work has suggested that other cereals do not have orthologues of ZmMRP-1, our work suggests OsIAA29 and OsMRPLs and their homologues in other grasses are part of an auxin-regulated, conserved signalling network involved in the differentiation of cells with ETC-like function in developing cereal grains.
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