Agriculture Reference
In-Depth Information
MADS box genes
( LeMADS-RIN , FaMADS9 , etc.)
Other
hormonal
regulation?
Other
transcription
factor?
Signal for maturation and ripening
?
ABA
Ethylene
Ethylene-independent
gene expression
Ethylene-dependent
gene expression
Non-climacteric type
Climacteric type
Ripening
Fig. 1.2. Summary of the ripening regulation in climacteric and non-climacteric fruits.
the control fruit (Sun et al. , 2012a,b). A
similar enhancement of ethylene pro-
duction was observed in an ABA-defi cient
mutant in orange fruit (Alferez and
Zacarias, 1999). These results suggest that
ABA plays a partial role in fruit ripening
and ethylene production or that the
remaining ABA is suffi cient to trigger
ethylene synthesis.
Brassinosteroids (BRs) are steroidal
plant hormones that are essential for
normal plant development and affect pro-
cesses such as cell elongation, cell division,
vascular differentiation, reproductive de-
velopment, and pathogen and abiotic
tolerance (Clouse, 2002). The involvement
of BRs in fruit ripening remains unclear.
However, Symons et al. (2006) reported that
endogenous BR levels increase in
association with ripening in grape, and the
ripening process is promoted by exogenous
BRs and delayed by an inhibitor of BR
biosynthesis. Exogenous BRs promote the
ripening processes in the same manner in
tomato (Vardhini and Rao, 2002). Although
the evidence implicating a role of BRs in
fruit ripening has been inconclusive, a
possible role for BRs in fruit ripening may
be revealed by further studies.
Auxin has been proposed to function as
a negative regulator of fruit ripening in a
number of climacteric and non-climacteric
fruits, including avocado (Tingwa and
Young, 1975), pear (Frenkel and Dyck,
1973), grape (Coombe and Hale, 1973;
Davies et al. , 1997) and strawberry (Given
et al. , 1988). For example, exogenous auxin
treatments delay the onset of ripening in
these fruits. In strawberry, the expression
levels of genes for polygalacturonase and
expansin, which are related to cell-wall
degradation, were shown to be repressed
by auxin (Villarreal et al. , 2008; Figueroa et
al. , 2009). In grape, auxin treatment delays
the expression of a number of ripening-
related genes (Davies et al. , 1997).
Similar to auxin, gibberellin (GA) has
been implicated to have a negative
regulatory role in the ripening process.
Certain studies have described the function
of GA in fruit ripening. In strawberry, GA
has inhibitory effects on fruit ripening,
 
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