Changes in the xylem exudate composition of poplar Populus tremula x P. alba)-dependent on the nitrogen

Multi-omics analysis of xylem sap uncovers dynamic modulation of poplar defenses by ammonium and nitrate

“…Taken together, glutamine and glutamate accumulated more than twelve-fold under high compared to low ammonium supply but only up to six-fold under high compared to low nitrate supply. Other studies found that glutamine is the major amino acid in poplar xylem sap (Dickson et al, 1985;Siebrecht & Tischner, 1999). Furthermore, ammonium and nitrate nutrition caused alterations in carbon-bearing compounds in the xylem sap: soluble carbohydrate levels were approximately twofold higher in high ammonium-than in high nitrate-fed plants (Figure 1b).…”

“…In addition to inorganic N, amino acids play a major role as a transport form of N in the xylem sap (Grassi et al, 2002). In poplars under field and laboratory conditions, glutamine is generally the most abundant xylem sap amino-N form (Dickson et al, 1985;Escher et al, 2004;Siebrecht and Tischner, 1999). In our study, glutamic acid-based amino acids dominated as well, but the fractions of glutamine and glutamate in xylem sap could not be distinguished because of cyclization of glutamate and glutamine to pyroglutamic acid (Purwaha et al, 2014) that happened during derivatization prior to GC-MS analysis applied here (Supporting Figure S2).…”

“…The consequences of variations in nitrate or ammonium nutrition have been studied in leaves and roots showing, for example, stronger responses to ammonium than to nitrate depletion in Arabidopsis leaves (Menz et al, 2016). N transport in xylem sap has been studied in tree species focusing mainly on amino acids, nitrate, and ammonium (e.g., Gessler et al, 1998Gessler et al, , 2004Kato, 1981;Siebrecht & Tischner, 1999;Tromp & Ovaa, 1976;Weber et al, 1998). Poplar (Populus x canescens) xylem sap contains approximately 3 mM nitrate and up to 15 mM glutamine, when fed with 1 mM NO3in hydroponics (Siebrecht and Tischner, 1999).…”

“…N transport in xylem sap has been studied in tree species focusing mainly on amino acids, nitrate, and ammonium (e.g., Gessler et al, 1998Gessler et al, , 2004Kato, 1981;Siebrecht & Tischner, 1999;Tromp & Ovaa, 1976;Weber et al, 1998). Poplar (Populus x canescens) xylem sap contains approximately 3 mM nitrate and up to 15 mM glutamine, when fed with 1 mM NO3in hydroponics (Siebrecht and Tischner, 1999). After switching from nitrate to ammonium nutrition, nitrate concentrations in the xylem sap of poplar drop quickly and NH4 + levels increase (Siebrecht and Tischner, 1999).…”

“…Poplar (Populus x canescens) xylem sap contains approximately 3 mM nitrate and up to 15 mM glutamine, when fed with 1 mM NO3in hydroponics (Siebrecht and Tischner, 1999). After switching from nitrate to ammonium nutrition, nitrate concentrations in the xylem sap of poplar drop quickly and NH4 + levels increase (Siebrecht and Tischner, 1999). In addition to mineral nutrients and amino acids,…”