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Yali He, Xiaozhong Liu, and Bingru Huang

The acclimation of plants to moderately high temperature plays an important role in inducing plant tolerance to subsequent lethal high temperatures. This study was performed to investigate the effects of heat acclimation and sudden heat stress on protein synthesis and degradation in creeping bentgrass (Agrostis palustris Huds.). Plants of the cultivar Penncross were subjected to two temperature regimes in growth chambers: 1) heat acclimation—plants were exposed to a gradual increase in temperatures from 20 to 25, 30, and 35 °C for 7 days at each temperature level before being exposed to 40 °C for 28 days; and 2) sudden heat stress (nonacclimation)—plants were directly exposed to 40 °C for 28 days from 20 °C without acclimation through the gradual increase in temperatures. Heat acclimation increased plant tolerance to subsequent heat stress, as demonstrated by lower electrolyte leakage (relative EL) in leaves of heat-acclimated plants compared to nonacclimated plants at 40 °C. Heat acclimation induced expression of some heat shock proteins (HSPs), 57 and 54 kDa, detected in a salt-soluble form (cystoplasmic proteins), which were not present in unacclimated plants under heat stress. However, HSPs of 23, 36, and 66 kDa were induced by both sudden and gradual exposure to heat stress. In general, total protein content decreased under both heat acclimation and sudden heat stress. Cystoplasmic proteins was more sensitive to increasing temperatures, with a significant decline initiated at 25 °C, while sodium dodecyl sulphate (SDS)-soluble (membrane) protein content did not decrease significantly until temperature was elevated to 30 °C. The results demonstrated that both a gradual increase in temperature and sudden heat stress caused protein degradation and also induced expression of newly synthesized HSPs. Our results suggested that the induction of new HSPs during heat acclimation might be associated with the enhanced thermotolerance of creeping bentgrass, although direct correlation of these two factors is yet to be determined. This study also indicated that protein degradation could be associated with heat injury during either gradual increases in temperature or sudden heat stress.

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Allan B. Woolf and Michael Lay-Yee

`Hass' avocados [Persea americana Mill.] were pretreated in water (38 °C for up to 120 min) immediately before 50 °C hot water treatments of up to 10 min. Fruit were stored for 1 week at 6 °C and ripened at 20 °C. External browning was evaluated immediately upon removal from cold storage, and fruit quality evaluated when fruit were ripe. Pretreatments at 38 °C tended to reduce the levels of external browning, skin hardening, and internal disorders, such as tissue breakdown and body rots, that were associated, and increased, with longer hot water treatments. A pretreatment of 60 min was the most effective for eliminating external browning, and reducing hardening of the skin when fruit were ripe following hot water treatment. Examination of heat shock protein (hsp) gene expression in avocado skin tissue, showed that levels of hspl7 and hsp70 homologous mRNA increased with increasing pretreatment duration. The results demonstrate that 38 °C pretreatments increase the tolerance of avocado fruit to subsequent hot water treatments.

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Allan B. Woolf, Christopher B. Watkins, Judith H. Bowen, Michael Lay-Yee, John H. Maindonald, and Ian B. Ferguson

`Hass' avocados (Persea americana Mill.) were heated in air at 25 to 46C for 0.5 to 24 hours and stored at 0, 2, or 6C. After storage, fruit were ripened at 20C and their quality was evaluated. In unheated fruit, external chilling injury occurred in fruit stored at 0 or 2C, hut not 6C. Chilling injury was also evident after storage at 2C in fruit heated at 34C, and to a lesser extent in fruit heated at 36C. A heat treatment (HT) of 38C for 3, 6, or 10 hours and 40C for 0.5 hour further reduced external chilling injury induced by storage at 2C. These HTs did not reduce internal fruit quality and resulted in more marketable fruit than unheated fruit stored at 6C. Low-temperature storage and HT slowed avocado ripening, resulting in longer shelf life after storage. In flesh tissue sampled directly after selected HTs, the levels of mRNA homologous to cDNA probes for two plant heat-shock protein (HSP) genes (HSP17 and HSP70) increased to a maximum at 40C and declined at higher temperatures. These increases in gene expression coincided with the extent to which HTs prevented chilling injury. Hot-air HTs confer significant protection against low-temperature damage to avocados.

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Seenivasan Natarajan and Jeff S. Kuehny

heat-tolerant lines so that breeding programs can use these plants to improve the thermotolerance of new releases ( Prasad et al., 1999 ). Many organisms, including plants, accumulate heat shock proteins (HSP) in response to high nonlethal temperatures

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Hyesoon Kim and Yeh-Jin Ahn

stress. All living organisms, including plants, respond to heat stress (10 to 15 °C above their optimal growth temperatures) by producing a set of proteins called heat shock proteins (HSPs; Wahid et al., 2007 ). In eukaryotic organisms, HSPs are

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Mahalaxmi Veerasamy, Yali He, and Bingru Huang

involves induction of protein synthesis or altered protein functions ( Teeri, 1980 ). A family of proteins, called heat-shock proteins (HSPs), are often induced when plants are exposed to elevated temperatures. Heat-shock proteins are divided into two major

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Magaji G. Usman, Mohd Y. Rafii, Mohd Razi Ismail, Mohammad Abdul Malek, and Mohammad Abdul Latif

area of research. Heat shock proteins (HSPs), or stress proteins, are highly conserved and present in all plants and animals. Previous results revealed that most HSPs serve as molecular chaperones ( Bukau et al., 2006 ; Pratt et al., 2001 ). These

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Ben-Hong Wu, Ning Niu, Ji-Hu Li, and Shao-Hua Li

)], proteins involved in photosynthesis and heat shock proteins were less accumulated in the skin of berries subjected to sunlight exclusion, whereas proteins related to glycolysis, the tricarboxylic-acid cycle, protein synthesis, and biogenesis of cellular

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Chenping Xu, Zhongchun Jiang, and Bingru Huang

protein (XIP-I) accumulates in the grain and has homologues in other cereals J. Cereal Sci. 37 187 194 Feder, M.E. Hoffman, G.E. 1999 Heat-shock proteins, molecular chaperones, and the stress response: Evolutionary and ecological physiology Annu. Rev

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Zhou Li, Yan Peng, and Bingru Huang

drought condition. Expression of genes involved in stress-protective proteins and other metabolism affected by H 2 O 2 and Ca. Under well-watered condition, heat shock protein 90 ( HSP90 ) and MT1 expression were not changed by foliar application of H