( Harrison et al., 2001 ). In tomato, 18 EXP members have been identified. Le-EXP1 expressed specifically in the ripening fruit ( Rose et al., 1997 ). Its important role in ripening of tomato fruit was noted by Brummell et al. (2002) . Overexpression
Shaolan Yang, Changjie Xu, Bo Zhang, Xian Li, and Kunsong Chen
Alexander G. Litvin, Marc W. van Iersel, and Anish Malladi
Drought stress reduces stem elongation and cell expansion. Since gibberellins (GAs) play an important role in controlling cell elongation, the objective of this study was to determine if the reduction in growth under drought stress is associated with altered GA metabolism or signaling. We exposed ‘Moneymaker’ tomato (Solanum lycopersicum) to drought stress to observe the effects on growth. Irrigation was automated using a data logger, which maintained volumetric water contents (VWC) of 0.35 and 0.15 m3·m−3 for well-watered and drought-stressed conditions, respectively. To further investigate the effect of GAs on elongation, paclobutrazol (PAC), a GA biosynthesis inhibitor, was applied to reduce endogenous GA production. Drought stress and PAC treatment reduced plant height. Internode length, cell size, and shoot dry weight displayed an interaction between the VWC and PAC treatments. The transcript levels of SlGA20ox1, -2, -3, and -4, SlGA3ox2, and SlGA2ox2, -4, and -5, corresponding to enzymes in GA metabolism, and LeEXP1, and -2, encoding expansin enzymes related to cell wall loosening necessary for cell expansion, were analyzed. Downregulation of transcript accumulation due to drought stress was observed for SlGA20ox4, SlGA2ox5, and LeEXP1, but not for any of the other genes. PAC increased expression of SlGA20ox-3, and SlGA3ox2, potentially through feedback regulation. These findings suggest that drought stress effects on elongation are at least partly mediated by altered GA metabolism.
Jorge A. Zegbe, M. Hossein Behboudian, Brent E. Clothier, and Alexander Lang
for 12 weeks and 18 d (Exp. 1) and 10 weeks and 16 d (Exp. 2). Fruit IEC is a physiological indicator of fruit maturity ( Graell et al., 1993 ; Mpelasoka et al., 2000 ). In Expt. 2, at harvest, the IEC tended to be higher in PRD fruit than in
Zhencai Wu and Paul A. Wiersma
Expansins are a class of proteins that stimulate the extension of plant cell walls. Expansins have been found in nearly all growing plant tissues, such as hycopotyls, young seedlings, fibers, internodes, flower petals, and ripening fruits. We isolated two full-length expansin cDNA clones, Pruav-Exp1 and Pruav-Exp2, from sweet cherry (Prunus avium L.) fruit. Pruav-Exp1 has 1048 nucleotides encoding 254 amino acids, while Pruav-Exp2 has 1339 nucleotides encoding 250 amino acids. Deduced amino acid sequences of sweet cherry Pruav-Exp1 and Pruav-Exp2 share 72% identity. A Blast search of the GenBank database with the deduced amino acid sequences of Pruav-Exp1 and Pruav-Exp2 indicated a high sequence identity with other plant expansin genes. Interestingly, Pruav-Exp1 shares 99% identity of amino acid sequence with that of apricot expansin Pav-Exp1. Fragments from the 3' ends of Pruav-Exp1 and Pruav-Exp2 were cloned to generate gene-specific probes. These probes were used to study expansin gene expression in different tissues and during fruit development. Northern blot analysis showed different mRNA expression patterns for each gene. The mRNA of Pruav-Exp1 was expressed at the pink and ripe stages, but not at the early green and yellow stages of fruit development. The mRNA of Pruav-Exp2 was present earlier, from a low level in yellow expanding fruit, increasing to a high level at the pink stage and remaining at this level through the ripe stage. Both mRNAs were also expressed at a low level in flower, but not present in other tissues such as roots, leaves and peduncles. Our study indicates an expansin gene family is present in sweet cherry and suggests that two expansin genes may have different roles during fruit development and ripening.
Kenton W. Peterson, Jack D. Fry, and Dale J. Bremer
× Z. pacifica ), Meyer ( Z. japonica ), and Chinese Common ( Z. japonica ) and the experimental progeny Exp1 ( Z. matrella × Z. japonica ), and Exp2 and Exp3 [( Z. japonica × Z. pacifica ) × Z. japonica ]. The experimental progeny have been
Benjamin G. Mullinix, Sharad C. Phatak, and Janet Cooper
Six tomato cultivars [Hotset, Petra, Stella, Big-O, Tropic, & Monte Carlo (fresh market)] were grown in a greenhouse in 1979 from July through November in 3 experiments. Exp. 1: The first two cultivars were used in a 15 cm, 30 cm, or 45 cm in-row spacing with rows spaced 60 cm apart. Cumulative fruit number and weight per unit area declined with increasing in-row spacing. Exp. 2: The first four cultivars were subjected to either cold or no cold treatment during germination before transplanting. No differences were found between the two treatments for mean fruit weight or total fruit number. Exp. 3: The last two cultivars were subjected to both the cold treatment and flower vibration. Cumulative fruit weight was greater for vibrated flowers. Greater mean fruit weight occurred earlier with cold treatment and declined significantly later in season, and was more pronounced in Tropic than Monte Carlo.
Yu-Xiong Zhong, Jian-Ye Chen, Hai-Ling Feng, Jian-Fei Kuang, Ruo Xiao, Min Ou, Hui Xie, Wang-Jin Lu, Yue-Ming Jiang, and He-Tong Lin
specific DIG-labeled probes. As shown in Fig. 2 , the three Dl-EXP mRNAs and three Dl-XET mRNAs accumulated in different patterns in aril tissues of longan fruit during storage. Dl-EXP1 mRNA decreased initially and increased slightly at Day 5, Dl
Jeffrey G. Williamson and D. Scott NeSmith
variance to determine treatment effects. Southern highbush experiments. Hydrogen cyanamide sprays were applied during bloom to 1-year-old containerized ‘Misty’ (Exp. 1), and ‘Misty’ and ‘Santa Fe’ (Exp. 2) southern highbush blueberry plants
Zhengke Zhang, Runshan Fu, Donald J. Huber, Jingping Rao, Xiaoxiao Chang, Meijiao Hu, Yu Zhang, and Nina Jiang
of expansin genes in persimmon (cv. Fupingjianshi) fruit, termed CDK-Exp1 and CDK- Exp2 (not the full length sequences), were cloned during fruit growth and ripening ( Tong et al., 2005 ). The objective of the present study was to identify the
Jiwon Jeong, James Lee, and Donald J. Huber
. This study included three experiments performed over a two-season period. In the first season, fruit were harvested at a preripe (¼ slip) stage of development (Exp. 1). The subsequent two experiments were performed during the following season using half