Agriculture Reference
In-Depth Information
N availability, whatever the type of N fertilization conditions (organic or
mineral). Such proteins include those directly involved in N metabolism
or those positioned at the interface between C and N metabolism during
plant growth and development [150,191,192]. It will be necessary there-
fore to identify new N-responsive genes through detailed analyses of tran-
scriptomic data sets [189], including using systems biology approaches
[109]. The analyses will be targeted specifi cally to N uptake, assimilation
and recycling in vegetative [165 and reproductive organs [193] at various
stages of plant development, using plants grown under different levels of
N fertilization. Systems biology consists in taking advantage of various
'omics' data sets including transcriptomics, proteomics and metabolomics
that can be further analysed in an integrated manner through the utilization
of various mathematical, bioinformatic and computational tools [192]. Ul-
timately, such integrated analyses may allow the identifi cation of the key
individual or common regulatory elements involved in the control of a
given biological process [157]. Such an approach, originally developed
for the model plant Arabidopsis by virtue of the wealth of information
available at the transcriptome level, when transferred to crops, may help
in identifying key master genes involved in the control of NUE. In paral-
lel, metabolomic studies are becoming more and more extensively used
for the high throughput phenotyping necessary for large scale molecular
and quantitative genetic studies aimed at identifying new candidate genes
involved in the control of plant productivity [194,195]. This has prompted
a number of groups, to focus their research efforts on developing data
integration tools for metabolic reactions that complement gene expres-
sion studies. Encouragingly, on the modeling side, an increasing number
of genome-scale metabolic models of plants have recently been released
[196,197]. Such metabolic models should help to unravel key reactions
and thus limit the steps required for the control of NUE, taking into ac-
count both tissue-specifi cities and environmental constraints.
Using the knowledge gained from these various systems biology ap-
proaches, it should then be possible to map the newly identifi ed genes
encoding regulatory proteins or enzymes, taking advantage of the recent
progress in crop genomics through the availability of both physical and
genetic high density maps and QTL or Meta-QTL genetic map positions
generated by the plant science community [186,198]. Comparative ge-
