"Frontmatter". In: Plant Genomics and Proteomics

mRNA S
TABILITY
In addition to regulation at the transcriptional level, posttranscriptional
mechanisms also play a fundamental role. The control of mRNA stability is
one of the forms of posttranscriptional regulation, and the stability of a par-
ticular mRNA determines, to a great extent, its steady-state levels. The half-
lives of mRNAs can vary over a wide range. General structural elements
found at the ends of the mRNA, as well as specific sequence elements located
within a transcript, can all contribute to the overall stability of the message.
Specific sequence elements involved in the control of mRNA stability
include: 
∑ Downstream element (DST) identified from the unstable small auxin-
up RNA (SAUR) transcripts 
∑ The light-responsive element 
∑ The 3¢ UTR involved in sugar repression
Although it is clear that unstable mRNAs contain instability sequences,
no discrete stabilizing determinant has been demonstrated to be responsible
for the long half-life of an extremely stable transcript in plant systems
(Gutierrez et al., 1999).
C
HEMICALLY
R
EGULATED
G
ENE
E
XPRESSION IN
P
LANTS
Understanding the developmental and physiological responses in plants can
be facilitated by the targeted expression or suppression of specific genes.
This is frequently achieved through the use of transgenic plants, and the
precise control of the regulation of the expression of the introduced gene in
both time and space is necessary. In this context an expression cassette
should have two features:
1. The inducer must be specific and nontoxic.
2. The target promoter should have a very low noninduced activity and
a high induced activity.
The characteristics of several chemically inducible systems have been
reviewed (Padidam, 2003) and are included in Table 5.3 from this source.