The Role of Calcium in Mediating SlIAAs Expression in Tomato Pedicel Explants

In order to illuminate the effect of calcium on the IAA signal transduction,we studied the expression of eight SlIAA genes which were up-regulated by calcium during the abscission after short-term（1 h） and long-term（16 h） treatments with calcium,IAA and calcium inhibitors.The results indicated that calcium induced SlIAAs expression in 1 h at low concentration,EGTA affected little SlIAAs expression;it also increased IAA-induced transcript level of SlIAAs,TFP（named trifluoperazine） decreased most SlIAAs expression below the level of calcium combined with IAA-induced expression,except for SlIAA17.Long-term treatment of calcium or calcium inhibitors suppressed some SlIAAs expression,whereas TFP enhanced all SlIAAs expression.Interestingly,SlIAA29 was induced by most treatments excluding 16 h EGTA.

Correlation Between Endogenous Hormones of Stem Apices and Fruit Locule Numbers in Tomatoes During Floral Bud Differentiation Stages

The study was designed to elucidate the changes in the endogenous hormones of stem apices in tomatoes and the function of correlative endogenous hormones in tomatoes during floral bud differentiation stages. The tomato parents were crossed and reverse crossed by using two inbred lines of multi-locule （MLK1） and few-locule （FL1） with significant difference, and the relationship between endogenous hormones GA3, IAA, and ABA levels and ovary locule numbers of parents and progeny during floral bud differentiation initial stage, floral bud differentiation stage, sepal petal formation stage, carpel formation initial stage, and ovary locule complete formation stage was studied. GA3 levels in P1, P2, F1, and RF1 were consistent with locule numbers, and IAA and ABA levels were reverse to ovary locule numbers during the key stage. The correlation showed that, during sepal petal formation stage, the ovary locule numbers were positively correlated with GA3, GA3/IAA, and GA3/ABA, and were negatively correlated with IAA and ABA. It was speculated that increasing GA3 levels or decreasing IAA and ABA levels of stem apices in tomato might be able to enhance ovary locule numbers. The sepal petal formation stage was an important stage which regulated endogenous hormones in the ovary locule formation.

Effects of abiotic stress and hormones on the expressions of five13-CmLOXs and enzyme activity in oriental melon(Cucumis melo var.makuwa Makino)

Lipoxygenases（LOXs） are a group of non-heme,iron-containing enzymes and extensively involved in plant growth and development,ripening and senescence,stress responses,biosynthesis of regulatory molecules and defense reaction.In our previous study,18 LOXs in melon genome were screened and identified,and five 13-LOX genes（CmLOX08,CmLOX10,CmLOX12,CmLOX13 and CmLOX18） were predicted to locate in chloroplast.Phylogenetic analysis result showed that the five genes have high homology with jasmonic acid（JA） biosynthesis-related LOXs from other plants.In addition,promoter analysis revealed that motifs of the five genes participate in gene expression regulated by hormones and stresses.Therefore,we analyzed the expressions of the five genes and LOX activity in leaves of four-leaf stage seedlings of oriental melon cultivar Yumeiren under abiotic stress：wounding,cold,high temperature and hydrogen peroxide（H_2O_2）,and signal molecule treatments：methyl jasmonate（MeJA）,abscisic acid（ABA） and salicylic acid（SA）.Real time qPCR revealed that wounding and H_2O_2 induced the expressions of all the five genes.Only CmLOX08 was induced by cold while only CmLOX13 was suppressed by high temperature.ABA induced the expressions of CmLOXIO and CmLOX12 while inhibited CmLOX13 and CmLOX18.MeJA increased the 3 genes expressions except CmLOX08 and CmLOX13,whereas SA decreased the effect,apart from CmLOX12.All the abiotic stresses and signal molecules treatments increased the LOX activity in leaves of oriental melon.In summary,the results suggest that the five genes have diverse functions in abiotic stress and hormone responses,and might participate in defense response.The data generated in this study will be helpful in subcellular localization and transgenic experiment to understand their precise roles in plant defense response.

Change in ^(14)C-soluble Sugar Involved in the Photosynthate Translocation Pathway of Tomato

Liaoyuanduoli tomato was planted in pots in a solar greenhouse. The first leaf below the second cluster was labeled by ^14CO2 with a dose of 0.555 MBq 30 days after the second cluster anthesis. Mesophyll, midrib, petiole vascular of the fed leaf, internode vascular below the fed leaf （adjacent to the fed leaf）, peduncle vascular of the second cluster, sepal, fruit pedicle, pulp, pectinic, and dissepiment were taken 2, 4, 8, 12, 20, 24, 48, and 72 h, respectively, after ^14CO2 feed to determinate the composition and specific activity of carbohydrate at different sites and different time after the labeling. The results indicated that almost all of the photosynthates resulting from 1 h of photosynthesis could be transported out of the leaf within 72 h and more than 85% of them were exported within 24 h. The greatest amount of sucrose transport occurred in the internode pedicel vascular bundle 8 h after the start of photosynthesis. Assimilates entering the fruit through the internode and pedicel vascular bundles were detectable but in small quantities 2 h after photosynthesis. Only the radio activity of sucrose but not that of glucose and fructose was detected, suggesting that some of the sucrose in the fruit came directly through the phloem at an early stage of fruit development, not through the synthesis of glucose and fructose. Fruit vascular may be the part where sucrose first metabolized after it entered the fruit.

Tomato Key Sucrose Metabolizing Enzyme Activities and Gene Expression Under NaCl and PEG Iso-Osmotic Stresses

Changes in sucrose metabolism in response to salt （NaC1） and water （polyethylene glycol, PEG6000） iso-osmotic stresses were measured in tomato cultivar Liaoyuan Duoli （Solanum lycopersicum L.） and the objective was to provide a new evidence for the relationship between salt and osmotic stresses. The carbohydrate contents, as well as sucrose metabolizing enzymes activities and transcript levels were determined. The results indicated that soluble sugar and hexoses accumulated to higher levels and the contents of sucrose and starch were lower in mature fruit under the two stress treatments. Salt and water stresses can enhance the invertase and sucrose synthase activities of tomato fruit in a long period of time （45-60 days after anthesis）, and elevate the expression of soluble acid invertase mRNA. It showed that two different stresses could also regulate the soluble acid invertase activity by controlling its gene expression. The activity of sucrose synthase was linked to the changes in soluble sugar levels but not with transcript levels. The effects of salt and water stress treatments on sucrose phosphate synthase activities were weak.

Alteration of Sl YABBY2b gene expression impairs tomato ovary locule number and endogenous gibberellin content

Tomato is an ideal model species for fleshy fruit development research. Sl YABBY2 b regulates the ovary locule number, which is increased by gibberellins, in tomato. However, the relationship between Sl YABBY2 b and endogenous gibberellin is poorly understood. In this study, Sl YABBY2 b-overexpressing and RNA interference(RNAi) transgenic tomato plants were used to elucidate the mechanism by which Sl YABBY2 b regulates the ovary locule number and endogenous gibberellin content in tomato. Sl YABBY2 b-overexpressing plants showed fewer locules and lower gibberellin content than the control plants. Contrasting results were found in the RNAi lines. Therefore, the Sl YABBY2 b gene negatively regulates tomato ovary locule number and endogenous gibberellin content. Furthermore, the expression of Sl YABBY2 b gene was remarkably higher than that of the wild type in the apical shoots of gibberellindeficient mutants. This showed that the gibberellins can inhibit the expression of Sl YABBY2 b gene negative regulation. Further study revealed that Sl YABBY2 b suppressed the expression of Sl GA20 ox1 and Sl GA3 ox2, but increased that of Sl GA2 ox1 and Sl GA2 ox5 in the apical shoots of Sl YABBY2 b-overexpressing plants, thereby reducing gibberellin content. Contrasting results were found in the RNAi lines. Our results showed that the Sl YABBY2 b gene was located on gibberellin signal transduction pathways, fed back regulation of the synthesis of gibberellin, and felt exogenous gibberellin signal to further regulate the formation of tomato locule.