Nitrogen Recycling and Remobilization Are Differentially Controlled by Leaf Senescence and Development Stage in Arabidopsis under Low Nitrogen Nutrition

Abstract

Five recombinant inbred lines (RILs) of Arabidopsis (Arabidopsis thaliana), previously selected from the Bay-0 3 Shahdara RIL population on the basis of differential leaf senescence phenotypes (from early senescing to late senescing) when cultivated under nitrogen (N)-limiting conditions, were analyzed to monitor metabolic markers related to N assimilation and N remobilization pathways. In each RIL, a decrease of total N, free amino acid, and soluble protein contents with leaf aging was observed. In parallel, the expression of markers for N remobilization such as cytosolic glutamine synthetase, glutamate dehydrogenase, and CND41-like protease was increased. This increase occurred earlier and more rapidly in early-senescing lines than in late-senescing lines. We measured the partitioning of 15 N between sink and source leaves during the vegetative stage of development using 15 N tracing and showed that N remobilization from the source leaves to the sink leaves was more efficient in the early-senescing lines. The N remobilization rate was correlated with leaf senescence severity at the vegetative stage. Experiments of 15 N tracing at the reproductive stage showed, however, that the rate of N remobilization from the rosettes to the flowering organs and to the seeds was similar in early-and late-senescing lines. At the reproductive stage, N remobilization efficiency did not depend on senescence phenotypes but was related to the ratio between the biomasses of the sink and the source organs.

Reproductive organs regulate leaf nitrogen metabolism mediated by cytokinin signal

“…1b). This result corresponded well to those of previous reports (Masclaux et al 2000;Diaz et al 2008). We used this alteration in amino acid profiling in a model experiment to elucidate the regulatory mechanisms of leaf amino acid metabolism.…”

“…1b) indicated that nitrogen compounds were remobilized to the sink tissues during the reproductive developmental stage. This change in amino acid profiling has been reported previously (Masclaux et al 2000;Diaz et al 2008). Conversely, other reports have shown an increase in leaf asparagine content during senescence (Lin and Wu 2004;Lea et al 2007).…”

Climate warming alters nitrogen dynamics and total non-structural carbohydrate accumulations of perennial herbs of distinctive functional groups during the plant senescence in autumn in an alpine meadow of the Tibetan Plateau, China

“…It has been shown that elevated autumn temperatures in cold regions can stimulate photosynthetic rates despite the natural shift in photoperiod that marks the beginning of the senescence period (Méthy et al, 1997). This affects the degradation of chlorophyll (Davison, 1991;Fracheboud et al, 2009), and therefore the onset of plant senescence through N and C dynamics (Diaz et al, 2008;Kröger et al, 2007). However, the potential effects of warming on this mechanism of senescence and its consequences for C uptake and allocation have received little attention in climate warming studies.…”

Metabolic Regulation of Leaf Senescence in Sunflower (Helianthus annuus L.) Plants

“…photosynthetic pigment level, protein content and CO 2 fixation rate) in primary leaves of sunflower plants grown for 42 days. The start of senescence in sunflower plants was associated with a considerable decrease in protein content and specific leaf masses referred as weight (Table 1 These changes may reflect alterations in N and C compound distributions as a consequence of N remobilization, the efficiency of which is related to the ratio between biomass in the sink and source organs (Wiedemuth et al, 2005;Diaz et al, 2008). Since chloroplasts contain the largest amounts of protein in leaves, their breakdown releases most of the nitrogen that is reused by other plant organs.…”