Reference "Initiation of shoot apical meristem in rice characterization of four SHOOTLESS genes"

Reference ID

6079

Title

Initiation of shoot apical meristem in rice characterization of four SHOOTLESS genes

Source

Development (Cambridge, England), 1999, vol. 126, pp. 3629-3636

Authors (6)

Satoh-N	Hong-S-K
Nishimura-A	Matsuoka-M
Kitano-H	Nagato-Y

Abstract

The regulatory mechanism of shoot apical meristem (SAM) initiation is an
important subject in developmental plant biology. We characterized nine
recessive mutations derived from four independent loci (SHL1-SHL4) causing the
deletion of the SAM. Radicles were produced in these mutant embryos. Concomitant
with the loss of SAM, two embryo-specific organs, coleoptile and epiblast, were
lost, but the scutellum was formed normally. Therefore, differentiation of
radicle and scutellum is regulated independently of SAM, but that of coleoptile
and epiblast may depend on SAM. Regeneration experiments using adventitious
shoots from the scutellum-derived calli showed that no adventitious shoots were
regenerated in any shl mutant. However, small adventitious leaves were observed
in both mutant and wild-type calli, but they soon became necrotic and showed no
extensive growth. Thus, leaf primordia can initiate in the absence of SAM, but
their extensive growth requires the SAM. An in situ hybridization experiment
using a rice homeobox gene, OSH1, as a probe revealed that shl1 and shl2
modified the expression domain of OSH1, but normal expression of OSH1 was
observed in shl3 and shl4 embryos. Accordingly, SHL1 and SHL2 function upstream
of OSH1, and SHL3 and SHL4 downstream or independently of OSH1. These shl
mutants are useful for elucidating the genetic program driving SAM initiation
and for unraveling the interrelationships among various organs in grass embryos.