Distinct changes in soybean xylem sap proteome in response to pathogenic and symbiotic microbe interactions

Senthil Subramanian,Oliver Yu,Carol Keyes,Un-Haing Cho

doi:10.1186/1471-2229-9-119

Abstract

BackgroundPlant systemic signaling characterized by the long distance transport of molecules across plant organs involves the xylem and phloem conduits. Root-microbe interactions generate systemic signals that are transported to aerial organs via the xylem sap. We analyzed the xylem sap proteome of soybean seedlings in response to pathogenic and symbiotic interactions to identify systemic signaling proteins and other differentially expressed proteins.ResultsWe observed the increase of a serine protease and peroxidase in the xylem sap in response to Phytophthora sojae elicitor treatment. The high molecular weight fraction of soybean xylem sap was found to promote the growth of Neurospora crassa in vitro at lower concentrations and inhibit growth at higher concentrations. Sap from soybean plants treated with a P. sojae elicitor had a significantly higher inhibitory effect than sap from control soybean plants. When soybean seedlings were inoculated with the symbiont Bradyrhizobium japonicum, the abundance of a xyloglucan transendoglycosyl transferase protein increased in the xylem sap. However, RNAi-mediated silencing of the corresponding gene did not significantly affect nodulation in soybean hairy root composite plants.ConclusionOur study identified a number of sap proteins from soybean that are differentially induced in response to B. japonicum and P. sojae elicitor treatments and a majority of them were secreted proteins.

Highlights

Plant systemic signaling characterized by the long distance transport of molecules across plant organs involves the xylem and phloem conduits
We recently identified a group of proteins and small phenolic molecules, that are essential for hypersensitive response (HR) cell death and resistance against P. sojae in certain soybean lines [20,21]
Collection of soybean xylem sap We analyzed the xylem sap proteome of soybean plants in an attempt to identify proteins potentially involved in systemic signaling during two different plant-microbe interactions: response to the fungal elicitor P. sojae wall glucan elicitor (WGE) and symbiotic association with B. japonicum

Summary

Introduction

Plant systemic signaling characterized by the long distance transport of molecules across plant organs involves the xylem and phloem conduits. Systemic signaling is characterized by the transport of various signal molecules for long (organ to organ) or short distances (cell to cell) to coordinate plant responses to developmental or environmental cues. These signal molecules may include plant hormones [3,7,8], proteins [9], RNAs [10,11], and small molecules [12,13]. The xylem stream primarily transports nutrients and water from the roots to the aerial organs of the plant; whereas the phloem stream primarily transports organic compounds resulting from photosynthesis in the leaves to other plant organs The composition of both (page number not for citation purposes)

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Conclusion