Gene expression in autumn leaves.
Two cDNA libraries were prepared, one from leaves of a field-grown aspen (Populus tremula) tree, harvested just before any visible sign of leaf senescence in the autumn, and one from young but fully expanded leaves of greenhouse-grown aspen (Populus tremula x tremuloides). Expressed sequence tags (ESTs; 5,128 and 4,841, respectively) were obtained from the two libraries. A semiautomatic method of annotation and functional classification of the ESTs, according to a modified Munich Institute of Protein Sequences classification scheme, was developed, utilizing information from three different databases. The patterns of gene expression in the two libraries were strikingly different. In the autumn leaf library, ESTs encoding metallothionein, early light-inducible proteins, and cysteine proteases were most abundant. Clones encoding other proteases and proteins involved in respiration and breakdown of lipids and pigments, as well as stress-related genes, were also well represented. We identified homologs to many known senescence-associated genes, as well as seven different genes encoding cysteine proteases, two encoding aspartic proteases, five encoding metallothioneins, and 35 additional genes that were up-regulated in autumn leaves. We also indirectly estimated the rate of plastid protein synthesis in the autumn leaves to be less that 10% of that in young leaves.
Bhalerao
Rupali
R
Umea Plant Science Center, Department of Plant Physiology, Umea University, 901 87 Umea, Sweden.
Keskitalo
Johanna
J
Sterky
Fredrik
F
Erlandsson
Rikard
R
Björkbacka
Harry
H
Birve
Simon Jonsson
SJ
Karlsson
Jan
J
Gardeström
Per
P
Gustafsson
Petter
P
Lundeberg
Joakim
J
Jansson
Stefan
S
D029681:Arabidopsis Proteins; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000378:metabolism; D019069:Cell Respiration / Q000235:genetics / Q000502:physiology; D019295:Computational Biology; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism; D030541:Databases, Genetic; D020224:Expressed Sequence Tags; D020869:Gene Expression Profiling / Q000379:methods; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D050356:Lipid Metabolism; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism; D010788:Photosynthesis / Q000235:genetics; D018515:Plant Leaves / Q000235:genetics* / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D032107:Populus / Q000235:genetics / Q000254:growth & development; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D012621:Seasons
D029681:Arabidopsis Proteins; C078410:ELIP protein, Arabidopsis; D010940:Plant Proteins; D018749:RNA, Plant; D008668:Metallothionein; D003546:Cysteine Endopeptidases; D016282:Aspartic Acid Endopeptidases