Analysis of mRNAs that Accumulate in Response to Low Temperature Identifies a Thiol Protease Gene in Tomato

Abscisic acid (ABA) increases the freezing tolerance of bromegrass (Bromus inermis Leyss) cell-suspension cultures at 23'C and elicits many metabolic changes similar to those observed during cold acclimation. lnduction and maintenance of freezing tolerance by ABA is accompanied by the expression of novel polypeptides and translatable RNAs. l h e objective of this study was to isolate and characterize ABA-responsive cDNAs associated with ABAinduced freezing tolerance in bromegrass cell cultures. Among the 16 ABA-responsive cDNA clones isolated, 9 were expressed only with ABA treatment, 7 showed increased transcript level, and 1 was transiently expressed. Cold responsiveness was determined in three clones with increased transcript levels and in the transiently expressed clone. Deacclimation of ABA-hardened cells was a relatively slow process, because all of the novel transcripts persisted for at least 7 d after cells were cultured in ABA-free medium.Preliminary sequencing of cDNAs has identified several clones that share high sequence homology with genes associated with sugar metabolism, osmotic stress, and protease activity. Clone pBCA61 was fully sequenced and tentatively identified as an NADPHdependent aldose reductase. l h e predicted amino acid sequence of the coding region shared 92% similarity with that predicted for barley aldose reductase cDNA. It is proposed that expression of genes related to sugar metabolism and osmotic stress may be required for ABA-induced hardening.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Molecular Cloning of Abscisic Acid-Responsive mRNAs Expressed during the Induction of Freezing Tolerance in Bromegrass (Bromus inermis Leyss) Suspension Culture

Lee¹,

Chen²

1993

“…A number of putative thiol proteases have been identified from the sequence of cDNAs isolated from various plants. In tomato (Lycopersicon esculentum) fruit, a putative enzyme, C14, accumulates in response to low temperatures (31). A different thiol protease-encoding mRNA, COT44, accumulates in the vascular tissue and the epidermis of Brassica napus seedlings (9).…”

mentioning

confidence: 99%

Purification and Characterization of Aleurain

Holwerda

Rogers²

1992

Barley (Hordeum vulgare L. cv Himilaya) aleurain is a vacuolar thiol protease originally isolated as a cDNA with 65% derived amino acid sequence identity with cathepsin H (JC Rogers, D Dean, GR Heck [1985] Proc NatI Acad Sci USA 82: 6512-6516). We purified aleurain from barley leaves to homogeneity (>1000-fold) and characterized its activity against a number of substrates. Aleurain is best described as an aminopeptidase; it hydrolyzes three different aminopeptidase substrates with similar catalytic efficiency but is less efficient at hydrolyzing an NH2-blocked substrate analog and azocasein. Our values for Km and kcat for three substrates (arginine 4-methyl-7-coumarylamide, L-arginine,6-naphthylamide, and N-a-benzoyl-L-arginine #-naphthylamide) and specific activity with azocasein are all within a threefold range of those previously reported for human cathepsin H for these substrates (WN Schwartz, AJ Barrett [1980] hordein (14).In addition to the enzymes connected with storage protein l

“…We previously reported the cloning and analysis of cDNAs representing mRNAs that accumulate following exposure of tomato fruit to 4°C (30). The concentration of two of these mRNAs increased relatively rapidly in response to low temperature and decreased upon removal ofthe stress.…”

mentioning

confidence: 99%

“…Exposure to low nonfreezing temperature causes accumulation of specific mRNAs in tomato fruit (30) and alfalfa (26), and elicits alterations in protein profiles from in vitro translated RNA of barley (4), Arabidopsis (13,18), rapeseed (25), and spinach (15).…”

mentioning

confidence: 99%

Transcriptional Activation by Heat and Cold of a Thiol Protease Gene in Tomato

Schaffer¹,

Fischer²

1990

Self Cite

We previously determined that low temperature induces the accumulation in tomato (Lycopersicon esculentum) fruit of a cloned mRNA, designated C14, encoding a polypeptide related to thiol proteases (MA Schaffer, RL Fischer [1988] Plant Physiol 87: 431-436). We now demonstrate that C14 mRNA accumulation is a response common to both high (400C) and low (40C) temperature stresses. Exposure of tomato fruit to 400C results in the accumulation of C14 mRNA, by 8 hours. This response is more rapid than that to 40C, but slower than the induction of many heat shock messages by 400C, and therefore unique. We have also studied the mechanism by which heat and cold exposure activate C14 gene expression. Both high and low temperature regulate protease gene expression through transcriptional induction of a single C14 gene. A hypothesis for the function of C14 thiol protease gene expression in response to heat and cold is discussed.Many plants commonly grown (2, 5), a signal for proteolysis of damaged proteins (16). Other heat shock proteins, although not known to be directly involved in protein degradation, appear to play related roles, by maintaining normal protein conformations or protein-protein interactions without stress, and by preventing aggregation ofabnormally folded proteins during heat stress (23).To learn whether induction of C14 thiol protease gene expression might constitute a mechanism common to a plant's response to both high and low temperature stress, we investigated the effect of high temperature on C14 gene expression in tomato fruit. Results show that heat shock induces accumulation of thiol protease mRNA and that this induction is more rapid than that by cold, but different from the classical heat shock response. We also demonstrate that transcriptional processes regulate C14 gene expression in response to both high and low temperature treatments. MATERIALS AND METHODS Exposure of Plant Material to Low and High TemperatureTomato (Lycopersicon esculentum cv VFNT Cherry) plants were grown under standard greenhouse conditions. Mature green fruit were incubated upon harvest in a darkened growth chamber for 16 h at 22°C, followed by treatment at either 4, 22, or 40'C for indicated times.