Paul Nadeau

Effect of photochemical treatment in the preservation of fresh tomato (Lycopersicon esculentum cv. Capello) by delaying senescence

Abstract The effect of hormic dosage of ultraviolet radiation in delaying the senescence of tomato was investigated. Mature-green tomato fruit (var. Capello) were irradiated with ultraviolet light (UV-C, 200–280 nm) corresponding to 0, UV–3.7×103 J m−2 and UV-24.4×103 J m−2, and were stored at 16°C, under high relative humidity for a period of 35 days. Attributes of senescence such as weight loss, color, texture, respiration rate, ethylene production and putrescine were monitored periodically throughout the storage period. A dose of UV-3.7×103 J m−2 was found to be beneficial (hormic) in delaying ripening and senescence, while the higher dose impaired ripening and caused abnormal browning, manifested as sun-scalding of the fruits surface. The development of color and softening of tissue were significantly retarded during storage in response to the treatment with the hormic dose (UV-3.7×103 J m−2). In addition to a delay in the climacteric response by at least 7 days, the respiration rate and ethylene production of the treated fruit were also reduced. The delay in senescence was attributed in part, to the maintenance of a high level of putrescine (antisenescence agents exerting opposite physiological effect to ethylene). The results suggest that photochemical treatment may have potential for preservation of fresh fruit and vegetables.

Raffinose and Stachyose Accumulation, Galactinol Synthase Expression, and Winter Injury of Contrasting Alfalfa Germplasms

been identified in alfalfa (Mohapatra et al., 1989; McKersie et al., 1993; Monroy et al., 1993, 1998; Wolfraim et Large differences in winter hardiness exist among alfalfa (Medicago al., 1993; Castonguay et al., 1994; Monroy and Dhindsa, sativa L.) cultivars, but the physiological and molecular bases for 1995), the function of these genes in planta and their these differences are not understood. Our objective was to determine how raffinose family oligosaccharide (RFO) accumulation and steady relationship with fall dormancy and winter hardiness is state mRNA levels for galactinol synthase (GaS) in roots relate to not understood. genetic variation in alfalfa winter survival. A GaS cDNA was isolated Several physiological processes also have been associthat possesses over 70% identity with GaS clones from other plant ated with improved winter hardiness of alfalfa. For despecies. Induction of GaS transcripts in crowns of winter hardy alfalfa cades, the accumulation of starch and soluble sugars in cultivars occurred within 8 h of exposure to 2 C, and was intensified roots has been the focus of research (Graber et al., 1927; by exposing plants to 2 C for 2 wk. Galactinol synthase transcripts Grandfield, 1943; Smith, 1964). Initially, it was believed increased in November in crown and root tissues of winter hardy that the accumulation of total nonstructural carbohyalfalfa plants. This increase was accompanied by large increases in drates (TNC, sum of sugar and starch concentrations) root RFO concentrations between October and December. A close in roots was critical to successful overwintering and subpositive association between RFO accumulation in roots in December and genetic differences in winter survival was observed in these alfalfa sequent spring growth of this perennial species. Later, populations. Although roots and crowns of nondormant alfalfa cultiit was shown that soluble sugars accumulated in alfalfa vars accumulated both GaS transcripts and RFO, accumulation was roots and crowns as plants hardened for winter (Bula delayed until December and these cultivars did not survive winter. et al., 1956; Ruelke and Smith, 1956), but how sugar Understanding the mechanisms regulating GaS gene expression and accumulation affected genetic differences in winter harsubsequent RFO accumulation in roots and crowns provides opportudiness was not studied. Recently, we have shown that nity to genetically improve alfalfa winter hardiness. sugar concentrations are consistently lower in roots of nondormant alfalfa cultivars when compared with fall dormant, winter hardy alfalfa cultivars (Cunningham V differences in winter hardiness exist among and Volenec, 1998). alfalfa (Medicago sativa L.) cultivars, but the physiCastonguay et al. (1995) reported that sucrose, stachyological and molecular bases for these differences are ose, and raffinose accumulated in alfalfa roots, while not understood. From a morphological standpoint, fall concentrations of glucose, fructose, and starch declined dormancy reduces alfalfa shoot growth in autumn and during alfalfa cold acclimation. Further, differences in is associated with greater winter survival (Smith, 1961; the maximum level of freezing tolerance between nonStout, 1985; Stout and Hall, 1989; Sheaffer et al., 1992). hardy and winter hardy cultivars were better related to However, fall dormant cultivars have slow shoot rethe capacity of the plants to accumulate stachyose and growth after defoliation, which reduces forage yield and raffinose than to accumulate sucrose. To understand overall agronomic performance in summer. Recent gemechanisms controlling fall dormancy and winter hardinetic evidence suggests that understanding the relationness better, we have studied alfalfa populations selected ship between fall dormancy and winter survival may for contrasting fall dormancy. These populations also enable us to devise schemes to improve winter hardiness differ in winter hardiness and several other traits includwhile simultaneously reducing fall dormancy (Brummer ing root sugar concentrations (Cunningham et al., 1998, et al., 2000). Although several cold-inducible genes have 2001). They permit study of discrete changes in physiology and gene expression associated with selection for contrasting fall dormancy and winter hardiness in a manS.M. Cunningham and J.J. Volenec, Dep. of Agronomy, Purdue Univ., West Lafayette, IN 47907-1150 USA; P. Nadeau and Y. Castonguay, ner not possible using traditional cultivars that differ Station de Recherches, Agriculture and Agri-Food Canada, 2560 Hofor many characteristics. We do not know if changes chelaga Blvd., Sainte-Foy, QC, Canada G1V 2J3; S. Laberge, Soils in sugar composition occurred as a result of genetic and Crops Research and Development Centre, Agriculture and Agriselection for contrasting fall dormancy in these germFood Canada, 2560 Hochelaga Blvd., Sainte-Foy, QC, Canada G1V plasms, and if expression of genes for key enzymes in2J3. This work was supported, in part, by USDA-IFAFS grant number 00-52100-9611. Contribution from the Purdue Univ. Agric. Exp. Stn., volved in RFO synthesis, such as galactinol synthase, Journal Series No. 16719. The authors acknowledge the contribution are associated with RFO accumulation and improved of Dr. L.R. Teuber at the University of California, Davis, who provided seed of the contrasting fall dormancy selections used in this Abbreviations: cDNA, complementary DNA; FD, fall dormancy; research. Received 24 Apr. 2002. Corresponding author (jvolenec@ GaS, galactinol synthase; HPLC, high pressure liquid chromatograpurdue.edu). phy; LSD, least significant difference; mRNA, messenger RNA; RFO, raffinose family oligosaccharides. Published in Crop Sci. 43:562–570 (2003).

A cold-induced gene from Medicago sativa encodes a bimodular protein similar to developmentally regulated proteins.

A new cold-regulated (COR) gene, msa CIC, was isolated by differential screening of a cDNA library from cold-acclimated crowns of alfalfa (Medicago sativa L. cv. Apica). Transcripts of msa CIC were not detectable in unacclimated alfalfa and accumulated to higher levels in cold-acclimated plants of the cold-tolerant cv. Apica than in those of the cold-sensitive cv. CUF-101. The DNA sequence analysis of a full-length cDNA clone revealed that msa CIC encodes for a putative protein (MSACIC) of 166 amino acids with distinct proline-rich and hydrophobic domains. Protein sequence comparisons indicated that MSACIC is similar to a group of bimodular proteins that are developmentally regulated in other plant species.

Differential accumulation of two glycine-rich proteins during cold-acclimation alfalfa.

Two mRNAs, MsaCiA and MsaCiB, encoding for proteins harboring glycine-rich motifs, accumulate in alfalfa during cold acclimation. Fusion polypeptides containing the amino acid sequences deduced from these mRNAs were produced in Escherichia coli and used to raise antibodies. Each antibody cross-reacted specifically with soluble polypeptides, MSACIA-32 and MSACIB, respectively. These polypeptides were detectable only in crowns of cold-acclimated plants, even though MsaCiA mRNA accumulated in both crows and leaves during cold acclimation. The analysis of parietal proteins showed that several MSACIA-related proteins, with a molecular mass of 32, 41 and 68 kDa, did accumulate in leaf cell walls and one of 59 kDa crown cell walls. This diversity is most probably due to a tissue-specific maturation of MSACIA. A discrepancy was found between the time-course of accumulation of MSACIB and the one of the corresponding transcript. These results indicate that timing and localization of MSACIA and MSACIB expression are different, and suggest that this differential expression involves both transcriptional and post-transcriptional events. Comparisons made among six cultivars of contrasting freezing tolerance suggest that low tolerance could be explained by failure to accumulate proteins like MSACIA and MSACIB at a sufficient level.

Differential Accumulation of Oligosaccharides and Freezing Tolerance of Alfalfa

Lack of winterhardiness severely reduces the persistence of alfalfa (Medicago sativa L.) under harsh winter conditions. The need to improve winterhardiness in lines of high agronomic value has been frequently pointed out (Buxton, 1989; Beuselinck et al., 1994). However, progress toward that goal is impeded by the multigenic nature of the trait and the lack of knowledge of the physiological and biochemical factors that determine winterhardiness. Cold tolerance is generally recognized as the most important component of winterhardiness (McKenzie et al., 1988). This is supported by the close relationship between the level of cold tolerance of cultivars acclimated under field conditions and their winterhardiness ranking (Paquin, 1984). Consequently, it is envisioned that improvement of cold tolerance will translate into superior field persistence of the cultivars (cvs).

In vitro translation products of mRNA from pericarp tissue of tomato cultivars differing in chilling tolerance

Abstract In vitro translation products from two tomato cultivars, Lycopersicon esculentum cv. ‘Early Cherry’ (‘EC’) and L. esculentum x L. pimpinellifolium cv. ‘New York 280’ (‘NY’), differing in chilling tolerance, were compared before and after 16 days of chilling at 4 °C, and after return of the fruit to 20 °C for one and five days. Ripening parameters, color and texture, were monitored during the experiments. Color development showed normal ripening of chill-tolerant ‘NY’ after the fruit were returned to 20 °C, but failure of chillsensitive ‘EC’ to ripen. Before chilling, slight differences in the patterns of translation products resolved by 2D-PAGE were observed between the two cvs. probably reflecting their different genetic background. Chilling induced changes in gene expression that were for a large part similar in fruit of both cvs. However, among responses that differed in the two cvs., changes in the levels of two low-molecular-weight basic translation products identified as ‘A’ (ca. 18 kDa, pH 8.0) and ‘B’ (ca. 14 kDa, pH 8.2) were most noticeable. Translation product ‘A’, faintly visible in ‘NY’ before chilling, was strongly expressed after 16 days of chilling and 24 h after transfer to 20 °C, but had disappeared five days after transfer to 20 °C. Translation product ‘A’ also increased in abundance in ‘EC’ at low temperature and was retained at appreciable levels five days after the fruit were returned to 20 °C. Translation product ‘B’ highly expressed in chilling-tolerant ‘NY’ before chilling, was sharply reduced in chilled fruit. This change was readily reversible upon transfer to 20 °C. By contrast, the level of polypeptide ‘B’ remained low in ‘EC’ under all treatments.