Polyamines and Regulation of Ripening and Senescence - Postharvest Biology and Technology of Fruits, Vegetables, and Flowers - page 332

Protein
stability

Protein biosynthesis
ribosomal stability

Protein
turn-over

Protein
degradation Amino acid

biosynthesis

Stress
response

Chaperone

Transcription

Ethylene
synthesis

Polyamines
Spd/Spm

Polyamine
biosynthesis

Ethylene
action

Transport

Signal transduction

Isoprenoid, carotenoid
Flavonoid biosynthesis

Nitrogen sensing/signaling
carbon metabolism

Respiration

Interactions
Possible interactions

Upregulated genes Upregulated metabolism

Downregulated metabolism Downregulated genes

Fig. 15.2 Diagrammatic representation of pathways/process regulated by Spd/Spm in tomato fruit as revealed
by macroarray analysis metabolic profiling in tomato. (Redrawn from Srivastava et al., 2007.)

A accumulated, while the levels of Val, Asp, sucrose, and glucose decreased in the red
transgenic fruit compared to the control red fruit. These results indicated that pathways
involved in nitrogen sensing/signaling and carbon metabolism are preferentially activated
in transgenics with high Spd/Spm but low Put (Mattoo et al., 2006). Transcriptome analyses
of these transgenics indicated upregulation of over 20% genes representing many different
anabolic pathways, supporting an anti-senescence role of PAs (Srivastava et al., 2007).
Most of the differentially expressed genes represented functional categories involved in
transcription, translation, signal transduction, chaperone activity, stress responses, amino
acid biosynthesis, ethylene biosynthesis and action, PA biosynthesis, and isoprenoid and
flavonoid biosynthesis. Figure 15.2 illustrates a composite of transcriptome analysis and
altered metabolite profiles. Taken together, these results show that PAs significantly enhance
anabolic pathways and thus may act as anabolic growth regulator(s) in plants (Mattoo et al.,
2007; Srivastava et al., 2007).

15.12 Concluding remarks

Biological revolution led by merging genetics with biotechnology and pyramiding of genes
is a promising development that will create designer crops with better quality (phytonutri-
ents), longer shelf life, and traits conferring resistance to postharvest pathogens and abiotic