L. Pnueli et al., THE TM5 MADS BOX GENE MEDIATES ORGAN DIFFERENTIATION IN THE 3 INNER WHORLS OF TOMATO FLOWERS, The Plant cell, 6(2), 1994, pp. 175-186
The tomato MADS box gene no. 5 (TM5) is shown here to be expressed in
meristematic domains fated to form the three inner whorls-petals, stam
ens, and gynoecia-of the tomato flower. TM5 is also expressed during o
rganogenesis and in the respective mature organs of these three whorls
. This is unlike the major organ identity genes of the MADS box family
from Antirrhinum and Arabidopsis, which function in overlapping primo
rdial territories consisting of only two floral whorls each. The devel
opmental relevance of the unique expression pattern of this putative h
omeotic gene was examined in transgenic plants. In agreement with the
expression patterns, antisense RNA of the TM5 gene conferred both earl
y and late alterations of morphogenetic markers. Early defects consist
of additional whorls or of a wrong number of organs per whorl. Late,
organ-specific changes include evergreen, cauline, and unabscised peta
ls; green, dialytic, and sterile anthers; and sterile carpels and defe
ctive styles on which glandular trichomes characteristic of sepals and
petals are ectopically formed. However, a complete homeotic transform
ation of either organ was not observed. The early and late floral phen
otypes of TM5 antisense plants suggest that TM5 mediates two unrelated
secondary regulatory systems. One system is the early function of the
floral meristem identity genes, and the other system is the function
of the major floral organ identity genes.