PJB-2014-242
MECHANISMS OF NITROGEN RE-DISTRIBUTION IN RESPONSE TO ENZYME ACTIVITIES AND THE EFFECTS ON NITROGEN USE EFFICIENCY IN BRASSICA NAPUS DURING LATER GROWTH STAGES
ZHENHUA ZHANG1,2*∆, WENMING WANG1∆, CHUNYUN GUAN3, QIANG LIU1,2, XIANGMIN RONG1,2, YONGLIANG HAN1,2, JIANGWEI PENG1,2, QIONG LIAO1, YING YU1 AND HAIXING SONG1,2*
Abstract
In order to investigate the mechanisms of nitrogen (N) re-distribution in response to proteolytic enzyme (PE), glutamine synthetase (GS) and glutamate synthetase (GOGAT) activities and the effects on N use efficiency (NUE). Two oilseed rape genotypes were grown in sand culture in a greenhouse under normal (15.0 mmol L-1 NO3-) and limited-N (7.5 mmol L-1 NO3-) levels. Isotope (15N) labeling and enzyme inhibitors against the PE, GS and GOGAT enzymes were used. We found that, when the two genotypes were subjected to specific inhibitors of PE, GS, and GOGAT, the activities of these enzymes were significantly decreased, resulting in reduced N re-distributed from leaf to grain, as well as reduced NUE. L-glutamine and free amino acid contents in the phloem sap were primarily influenced by PE and GS activities, whereas grain yield was primary regulated by GOGAT activity during the later growth stages. These findings suggest that PE, GS, and GOGAT are key enzymes for the regulation of N re-distribution in plant tissues during later growth stages, with grain yield and NUE of oilseed rape being positively regulated by PE, GS and GOGAT activities.
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