AtbZIP11 transcript levels are upregulated by both light and sugars, which contribute to photoassimilates availability as a result of photosynthesis. When carbohydratesupply is sufficient, sucrose-mediated repression of AtbZIP11 translation would be initiated. In this way, AtbZIP11 activity could keep carbohydrate homeostasis in plant . In contrast, the expression levels of AtbZIP1 and AtbZIP53 were induced after extended night treatment and repressed by sugars application . In strawberry, bZIP11 was induced by red and blue light, while bZIP53 homologue was depressed. In addition, sucrose treatment did not significantly affect bZIP53 at transcriptional level . These findings indicated that bZIP S1 members differentiated in response to some factors. All of bZIP S1 transcriptional factors have the SIRT-responsive uORFs, so researchers proposed a novel SIRT-bZIP technology to enhance sweetness especially for some plant species rich in sucrose . In our study, strawberry bZIP11 overexpressing in tomato indeed increased the TSS and SS content and SS/TA ratio, which provided an applicable method for improvement of strawberry and other fruit quality in the future. However, constitutive overexpression of FvbZIP11 caused a growth impairment, which have been observed in tobacco , Arabidopsis , banana . An explanation of this phenotype was that bZIP11 presumably severely affected carbohydrate partitioning via a mechanism that might include direct regulation to cell-wall invertase and sucrose transporter expression . To avoid growth impairment, Sagor et al. overexpressed SlbZIP1 and SlbZIP2 under the control of the fruit-specific E8 promoter. The growth and morphology of the resulting transgenic tomato plants were comparable to those of wildtype plants. Most fruit-specific promoters currently available have been isolated from tomato, but these promoters probably are inappropriate to be used in non-climacteric fruits, like strawberry . Hence, round planter pot identification of a suitable promoter could facilitate the function analysis of a specific gene involving fruit development and help to specifically improve fruit quality.
The rise of agriculture c. 7000 BC ensured a stable food supply, allowing human civilizations to develop and populations to grow . The challenge of feeding a growing population is exacerbated by climate unpredictability, with drought and temperature increases, leading to decreased crop yield . Tomato is by far the most widely grown vegetable crop worldwide . The narrow genetic base of most crops, combined with selection for performance under optimal conditions, has reduced the genetic variability in environmental stress responses, and the modern cultivars of tomato are no exception . The wild relatives of tomato have the genetic ability to adapt to extreme habitats, and many heirloom cultivars also retain this ability as a result of directed breeding with wild species, and less selection for commercially valuable traits . Heirloom tomatoes are defined as varieties, which have been passed down through multiple generations of a family . Improvement in tomato has focused on flowering, fruit traits, and disease resistance probably as a result of a perceived negative correlation between fruit size and sugar content . Thus, potential impacts of other factors on yield and fruit quality are relatively ignored . In a previous study by Chitwood et al. , a meta-analysis on a set of introgression lines linked leaf complexity and leaflet shape in tomato to fruit sugar content measured on the same lines by other researchers . This correlation showed that plants with complex and rounder leaflets also had increased fruit sugar content . Because leaves are the primary site of photosynthesis, it is possible that leaf shape changes may impact photosynthetic capacity and therefore result in different sugar content and yield in fruits. In addition to photosynthesis, sugar transport, and distribution to sinks are other potential sites of regulation in leaf function as source tissue. While sugar transport in plants is well described, distribution among different sink tissues is not fully understood .
We analyzed tomato cultivars with varied yield and fruit quality, photosynthetic capacity, leaflet shape, and other vegetative traits and found that leaflet shape was strongly correlated to overall fruit quality assessed as a composite measure of BRIX and yield , with rounder leaflets positively correlated with higher BY values. Photosynthesis, on the other hand, had a negative correlation with yield. Based on our analysis, leaf shape seems to play an important role in the distribution of photo assimilates. Additionally, we performed phylogenetic network analysis on 23 cultivars, including eight identified as having the rounder Potato Leaf Morph , known to be caused by a mutation in the C-locus , to determine their breeding histories and identify any potential selection for this trait.Eighteen heirloom tomato varieties identified as having a range of fruit types, including cherry and beefsteak tomatoes, and several intermediate types, were analyzed. These tomato varieties also differed in fruit production timing from early to late, and the type of leaf morphology. These cultivars were selected based on leaf shape as described in Tatiana’s TOMATO base and The Heirloom Tomato . Tomato seeds were treated, germinated, and field planted as previously described . In both the 2014 and 2015 seasons, plants were laid out in a randomized block design and were planted and grown in soil, with furrow irrigation once weekly.Gas exchange measurements were done in the field on attached leaves after the plants had recovered from transplanting. Measurements were made weekly from week 10 to week 15 , on week 17 , and weeks 18– 21 , on c. 60 plants each week, on three plants per cultivar wk–1 . Measurements were made on leaves from the upper and lower portions of the plants to eliminate positional bias within the plant, and measured for three leaves per plant. The A , gst , transpiration, and ɸPS2 of a 6 cm2 area of the leaflet were measured using the LI-6400 XT infrared gas exchange system , and a fluorescence head .
Light within the chamber was provided by the fluorescence head at 1500 µmol m2 s 1 photosynthetically active radiation , and the chamber air flow volume was 400 µmols s 1 with the chamber atmosphere mixed by a fan. CO2 concentration within the chamber was set at 400 µmols mol 1 . Humidity, leaf and chamber temperature were allowed to adjust to ambient conditions; however, the chamber block temperature was not allowed to exceed 36°C. Measured leaflets were allowed to equilibrate for 2–3 min before measurements were taken, allowing sufficient time for photosynthetic rates to stabilize with only marginal variation. The amount of intercepted PAR was measured in four orientations per plant and an average PARi calculated. PARi was measured by placing a Line Quantum Sensor onto a base made from ¼” PVC piping, and a Quantum Sensor approximately 1 m above the plant on the PVC rig. Measurements from both sensors were taken simultaneously for each sample using a Light Sensor Logger . This allowed variation in overall light intensities such as cloud movement to be measured and accounted for in the total PARi.After gas exchange measurements, three plants per cultivar were destructively harvested each week. The final yield and fresh vegetative weight of each plant harvested was measured using a hanging scale in the field. Five leaves were collected at random from the bottom and top of the plant to capture all canopy levels, round pot for plants and approximately nine fruit were collected for BRIX measurements. FW was used owing to the large number of plants and measurements being done in situ in the field setting. All measurements were made in kg. To measure the BRIX value of the tomatoes, the collected fruit was taken to the laboratory where the juice was collected and measured on a refractometer . The yield and BRIX for each plant were multiplied together to get the BRIX 9 yield index , which gives an overall fruit quality measure, accounting for variations and extreme values in either measurement. It should be noted that while BRIX is used as a standard quality measure, BY is a composite value that folds in yield to assess weight of soluble solids per plant and is being used to measure commercial quality and not consumer quality . BY measurements were done for both the 2014 and the more detailed 2015 fields. These data were compared to test for reproducibility of results .The leaf complexity measures included all leaflets present on the leaf. Subsequently, primary leaflets were used for imaging and analysis of shape and size as previously described , and the images then processed in IMAGEJ . The images were cropped to individual leaflets maintaining the exact pixel ratio of the original image, and then cropped again to only include the single leaflet using a custom Java script written for FIJI . Single leaflet images converted to a binary image as black on a white background, and smoothed to allow for the exclusion of any particulates in the image were then processed in R using MOMOCS, a shape analysis package. Leaflet images were imported and then aligned along their axes so that all images faced the same direction. They were then processed using elliptical Fourier analysis based on the calculated number of harmonics from the MOMOCS package. Principal component analysis was performed on the resulting eFourier analysis and the principal components were used for subsequent analysis. Traditional shape measures such as leaflet area, circularity, solidity, and roundness were done with the area measurement based on pixel density. These measures were compared with the PCs to determine the characteristics captured by each PC. The PC values were used for all subsequent leaflet shape and size analyses. Total leaf area for each plant was measured by imaging the whole plant and a 4 cm2 red square and then processed in the EASY LEAF AREA software .Five plants per line were used to analyze leaflet sugar content. The plants were grown under the same conditions as field plants with the following exceptions. Plants remained in the glasshouse after transfer to 1 gallon pots. All plants were watered with nutrient solution and grown until mature leaves could be sampled. Using a hole punch, a disk with an area of 0.28 cm2 was taken from the leaflets and extracted from the disks using a modi- fied extraction method from the Ainsworth laboratory . Leaf disks were placed in 2 mM HEPES in 80% EtOH and heated to 80°C for 20 min and the liquid collected and stored at placed in 2 mM HEPES in 50% EtOH and heated, collecting the 20°C. The entire process was repeated twice. They were then liquid and storing at 20°C followed by another 2 mM HEPES in 80% treatment. The collected liquid was then used to measure the amount of sugar present per area of disk. To measure leaf sugar content a working solution of 100 mM HEPES , 6.3 mM MgCl2 , and 3 mM ATP and NADP at pH 7 was prepared. From the working solution, an assay buffer was made adding 50 U of glucose-6-phosphate dehydrogenase , and 295 or 280 µl of the working solution was added to a 96-well plate for sucrose standards or samples, respectively. Standards were added at a 60-fold dilution and samples were added at a 15-fold dilution. Then 0.5 U of hexokinase , 0.21 U of phosphoglucoisomerase , and 20 U of invertase were added to each well and the plates allowed to sit overnight to reach equilibrium. The plates were measured on a UV spectrometer at 340 nm, followed by analysis in JMP .All statistical analyses were performed using JMP software. To determine statistical significance, measurements were modeled using general linear regression model and tested by a one-way ANOVA followed by Tukey’s honestly significant difference, if necessary. These modeled data for all measured values were compiled into a table and used to create a model using partial least-squares path modeling in SMARTPLS 3.0 . Modeled data were used for the statistical analyses as many measurement types varied in number of data points, and therefore a set of generated predicted values of equal size was used to make an equal data matrix . Partial least squares-PM was used to explore the cause-and-effect relationships between the measured variables through latent values. PLS-PM is effective in both exploring unknown relationships and combining large-scale data, such as field, physiological, and morphological data, that otherwise are not well described together .