The Glycine max Xylem Sap and Apoplast Proteome

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• 作者：Michael A. Djordjevic ; Marie Oakes ; Dong Xue Li ; Cheol Ho Hwang ; Charles H. Hocart ; Peter M. Gresshoff
• 刊名：Journal of Proteome Research
• 出版年：2007
• 出版时间：September 2007
• 年：2007
• 卷：6
• 期：9
• 页码：3771 - 3779
• 全文大小：474K
• 年卷期：v.6,no.9(September 2007)
• ISSN：1535-3907

文摘

Molecular signaling interactions in the plant apoplast are important for defense and developmentalresponses. We examined the soybean proteome of the apoplastic conduit of root-to-shoot communication, the xylem stream, using gel electrophoresis combined with two types of tandem massspectrometry. We examined soybeans for the presence of a Bradyrhizobium japonicum-induced, longdistance developmental signal that controls autoregulation of nodulation (AON) to determine if xylemproteins (XPs) were involved directly or indirectly in AON. The xylem and apoplast fluids collected inhypocotyl, epicotyl, and stem tissue contained a highly similar set of secreted proteins. The XPs weredifferent from those secreted from imbibing seed implying they play important basic roles in xylemfunction. The XPs of wild-type and nts1007 plants were indistinguishable irrespective of plant age,inoculation status, or time after inoculation suggesting that none was directly involved in AON. XPswere continuously loaded into the xylem stream, as they were present even 28 h after shoot decapitation.These results were consistent with semiquantitative RT-PCR studies that examined the expression ofgenes corresponding to the XPs under inoculated or uninoculated conditions. Monitoring the expressionof XP genes by RT-PCR showed that four possessed root biased expression. This suggested that thecorresponding protein products could be produced in roots and travel long distances to shoots. Ofthese, a species of lipid transfer protein is a candidate for a water-soluble, long-distance signal-carrierdue to the presence of hydrophobic clefts that bind known plant signals in vitro. Two soybean XPsidentified in this study, lipid transfer protein and Kunitz trypsin inhibitor (KTI), have known roles inplant signaling.