| Summary: | 碩士 === 國立中興大學 === 農業生物科技學研究所 === 87 === A recessive mutation affecting both root and shoot development was isolated
from transformants of lettuce cv. Diana co-transformed with maize Ac
transposase and Ds . All of the mutants were co-segregated with the T-DNA
containing Ac transposase indicating that the mutation was caused by
insertional mutagenesis. Mutations in this novel genetic locus, designated as
ABNORMAL ROOT AND SHOOT (ARS), showed a dwarf phenotype by
producing short thick roots,short hypocotyl and abnormal filamentous leaves
without any futher reproductive development . The anatomical analysis
revealed that the ars mutant root phenotype is primarily due to the lack of
cell elongation and to the abnormal increased cell numbers in the cortex region in the roots . ars mutants are able to initiate normal leaf primodia ,however the cell elongation and cellular organization of the developing leaf
primodia is impaired and results in sequentially abnormal development of the leaf. These findings indicate that the ARS gene represents a novel class of gene which is strictly required for cell elongation as well as cell orgnization
in the same type of cells after meristematic division in both the root and
shoot. ars mutants also display highly photomorphogenic development in
darkness by producing open cotyledons, developing vegetative leaves, and
short hypocotyls. This suggests that the ARS gene may also be involed in the
repression of photomorphogenic development in the absence of light. ars
mutations can not be normalized into wild-type plants by exogenous
application of phytohormones such as gibberllin(GA) or brassinosteriods,
indicating mutation is not likely impaired in the biosynthesis or perception of
these two hormones. A strategy based on IPCR was used to isolate a 356 bp
genomic DNA fragment flanking the insertional site of T-DNA. Using this
genomic DNA to futher clone ARS gene is in progress and will also be
presented.
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