PNNL-13501 - Pacific Northwest National Laboratory

putatively induced by artificial senescence conditions,
were identified and sequenced. Similarly, more than
20 novel clones were isolated from corn suppressive
subtractive cDNA library. When compared to other
known sequences via homology screening, gene
candidates putatively encode the following functionalities,
among others: photosynthesis, photorespiration, carbon
metabolism, nitrogen metabolism, proteases and protease
inhibitors, and aminotransferases.
Senescence-related responses were assessed by
completing Northern-blot assays on newly discovered
clones. Senescence conditions were simulated by cutting
leaf tissues from intact normal plants, then incubating
cuttings in DI water in the dark for up to 4 days. A
variety of responses were observed with the onset of
artificial senescence conditions, ranging from a rapid
accumulation of mRNA upon dark treatment to a gradual
accumulation of mRNA over the 4-day incubation
(Figure 2). Promoters from three separate potato clones
PSEN1, PSEN2, and PSEN3 were subsequently isolated
and sequenced.
Figure 2. Contrasting Northern blot assays completed using
senescence-active cDNA isolated from potato as probes.
Each lane corresponds to results seen at increasing days of
dark treatment post-abscission of potato leaves.
Summary and Conclusions
In this project, we isolated more than 50 unique gene
clones and 4 promoters, and provided detailed
characterization of the rpL34 promoter. The resulting
68 FY 2000 Laboratory Directed Research and Development Annual Report
molecular genetics knowledge will enable the
characterization of both meristematic as well as
senescence processes in relevant crop plants. These
advances may enable development of alternative uses of
high volume crops for renewable production of fuels and
chemicals, as well as the efficient sequestration of
airborne carbon in terrestrial plants.
References
Gao et al. 1994. Plant Mol Biol. 25:761-770.
Dai et al. 1996. Plant Mol Biol. 32:1055-1065.
Gan and Amasino 1995. Science. 270:1966.
Cramer et al. 1997. U.S. Patent 5689056.
Park et al. 1998. Plant Mol Biol 37:445.
Dai Z, B Hooker, R Quesenberry, DB Anderson, and
SR Thomas. 2000. Plant Mol Biol. (submitted).
Presentations
Shi L, Hooker BS, Quesenberry RD, An G, Dai Z. July
1999. “Functional analysis of promoter elements
controlling developmental and environmental regulation
of a tobacco ribosomal protein gene L34.” Presented at
the 1999 American Society of Plant Physiologists Annual
Meeting, Baltimore, Maryland.
Shi L, Hooker BS, Gao J, and Dai Z. July 2000.
“Isolation and Characterization of the Genomic DNA
Clones of Ribosomal Protein Gene L25 in Tobacco.”
Presented at the 2000 American Society of Plant
Physiologists Annual Meeting, San Diego, California.