Agriculture Reference
In-Depth Information
Expression correlation analysis in large-
scale transcriptome studies has resulted in
the identifi cation of a number of candidate
transcription factors that may control
cuticle assembly. Experiments in tomato
identifi ed orthologues of the Arabidopsis
SHINE and MIXTA-LIKE transcription
factors (Mintz-Oron et al. , 2008). The
Arabidopsis AtSHINE genes encode
APETALA2-domain proteins and primarily
regulate cutin biosynthesis genes (Shi et
al. , 2011). Functional characterization of
the tomato SHINE3 gene implicates this
transcription factor as a major regulator of
cuticle biosynthesis in tomato (Shi et al. ,
2013). Transgenic tomato lines reduced in
SHINE3 expression exhibit a severe
phenotype in the tomato peel, including
increased susceptibility to fungal partheno-
genesis and an increased rate of de-
hydration. The cuticles of transgenic lines
were signifi cantly thinner than those of the
wild type and showed a reduction of up to
40% in cutin monomers (Shi et al. , 2013).
A number of putative cutin biosynthesis
gene targets of SHINE3 are downregulated
in the transgenic lines and include: LACS2 ,
GPAT4 , CYP86A and GDSL1 . Shi et al.
(2013) suggested that SHINE3 is required
for cutin biosynthesis and possibly cutin
polymerization.
and transport will be a focus of future
work. The economic importance of
understanding these processes is clear
when one considers the scale of the fresh
fruit market and the impact that the cuticle
has on fruit quality. Mechanical failure of
the fruit cuticle can lead to considerable
economic loss for farmers through splitting
or cracking of the cuticle. Additionally, the
fruit surface is the major feature by which
the consumer is able to judge fruit quality.
Traits such as colour, glossiness, texture
and uniformity are all determined by the
cuticle. As our understanding of the
relationship between cuticle structure and
fruit surface characteristics advances, we
will increasingly be able to manipulate
these important traits. The range of
biological roles to which the fruit cuticle
contributes is extensive, and includes
sensitivity and response to biotic and
abiotic stresses as well as the development
of the mature fruit. Although char-
acterization of a number of genes and their
involvement in fruit cuticle biosynthesis
has begun, the genetics of fruit cuticle
biosynthesis still remains largely un-
characterized. Despite the limitations in our
understanding, current knowledge does
allow the molecular breeding and engin-
eering of many important traits into fruit.
Traits ranging from fruit quality and
aesthetics, such as shininess and shelf-life,
to agriculturally important traits, including
disease resistance and sensitivity to water
stress, are all associated with the cuticle.
Identifi cation of the key genes involved in
conferring these traits to fruit will provide
breeders with the ability to screen large
breeding populations for these important
genes. The traits can then be imported into
fruit lines through classical breeding or via
biotechnological methods. This has the
possibility of leading to improvements in
fruit production and quality.
6.6 The Applied Side of Fleshy Fruit
Cuticle Research and Future Prospects
The cuticle membrane of fl eshy fruit is a
highly specialized and complex layer.
Whilst we have a relatively good under-
standing of the biosynthesis and assembly
of the cuticle, we still have much to learn
about the regulation of cuticle biosynthesis.
It is likely that regulation of cuticle
biosynthesis together with solving the fi nal
problem of cutin oligomer polymerization
 
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