1. Differences between winter oilseed rape (Brassica napus L.) cultivars in nitrogen starvation-induced leaf senescence are governed by leaf-inherent rather than root-derived signals.
- Author
-
Koeslin-Findeklee F, Becker MA, van der Graaff E, Roitsch T, and Horst WJ
- Subjects
- Brassica napus genetics, Chlorophyll metabolism, Cytokinins metabolism, Gene Expression Regulation, Plant, Genes, Plant, Glucosides metabolism, Homeostasis, Peptide Hydrolases metabolism, Photosynthesis, Plant Leaves enzymology, Plant Proteins genetics, Plant Proteins metabolism, Signal Transduction genetics, Zeatin metabolism, Brassica napus metabolism, Nitrogen metabolism, Plant Leaves growth & development, Plant Leaves metabolism, Plant Roots metabolism, Seasons
- Abstract
Nitrogen (N) efficiency of winter oilseed rape (Brassica napus L.) line-cultivars (cvs.), defined as high grain yield under N limitation, has been primarily attributed to maintained N uptake during reproductive growth (N uptake efficiency) in combination with delayed senescence of the older leaves accompanied with maintained photosynthetic capacity (functional stay-green). However, it is not clear whether genotypic variation in N starvation-induced leaf senescence is due to leaf-inherent factors and/or governed by root-mediated signals. Therefore, the N-efficient and stay-green cvs. NPZ-1 and Apex were reciprocally grafted with the N-inefficient and early-senescing cvs. NPZ-2 and Capitol, respectively and grown in hydroponics. The senescence status of older leaves after 12 days of N starvation assessed by SPAD, photosynthesis and the expression of the senescence-specific cysteine protease gene SAG12-1 revealed that the stay-green phenotype of the cvs. NPZ-1 and Apex under N starvation was primarily under the control of leaf-inherent factors. The same four cultivars were submitted to N starvation for up to 12 days in a time-course experiment. The specific leaf contents of biologically active and inactive cytokinins (CKs) and the expression of genes involved in CK homeostasis revealed that under N starvation leaves of early-senescing cultivars were characterized by inactivation of biologically active CKs, whereas in stay-green cultivars synthesis, activation, binding of and response to biologically active CKs were favoured. These results suggest that the homeostasis of biologically active CKs was the predominant leaf-inherent factor for cultivar differences in N starvation-induced leaf senescence and thus N efficiency., (© The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.)
- Published
- 2015
- Full Text
- View/download PDF