Fig 1.
Phenotypic comparisons of the two upland cotton lines, immature fiber (im) mutant and its isogenic wild type, Texas Marker-1 (TM-1).
A. A field row of im plants. B. A field row of TM-1 plants. The length of a green garden stake used as a scale marker is 120 cm. C. The non-fluffy phenotype of the im boll. D. The fluffy phenotype of the TM-1 boll.
Table 1.
Fiber properties and leaf specific mass of the field-grown im and TM-1 plants.
Fig 2.
The fiber MIC of the NIL plants and the heat units during their active fiber development in the three field seasons.
A. Comparisons of MIC values between the im and TM-1 plants. Statistical significance at p < 0.0001 = ****. Error bar represents standard error of the mean. B. Heat units of three field seasons during active fiber development. Heat unit was determined by calculating growing degree days (GDD).
Fig 3.
Biomass of different organs of the NIL plants grown in greenhouse.
Each of the im or TM-1 plants was grown in a 14L pot with six replications. Average biomass of the whole plant as well as each type of organs including reproductive (bract, square, flower, boll and peduncle combined), root, petiole, leaf, and stem of the im plants were compared with TM-1. Two-way ANOVA showed a significant difference (p < 0.0001) in the total biomass between NIL plants. Error bar represents standard error of the mean. Biomass difference of each organ between the NILs was tested with t-tests and * above the bar indicates statistical significance (p < 0.05).
Fig 4.
Photosynthetic variables of the field-grown im and TM-1 plants at an optimum temperature.
Photosynthetic variables including (A) Fv/Fm, maximum quantum yield of PSII photochemistry, (B) Pnet, net photosynthesis, (C) E, transpiration rate (D) Ci, intercellular CO2 concentration, and (E) gs, stomatal conductance were measured from the leaf at the 18th node of the NILs at 31°C, within the range of the optimum temperature (28 ± 3°C). Error bar represents standard error of the mean. *, p < 0.05.
Fig 5.
Light response curves of net photosynthesis [Pnet] in the field-grown im and TM-1 plants.
Measurements were taken from the leaf at the 18th node, top canopy, of four replicate plants in each NIL at approximately 31°C with varying light intensity. Error bar represents ± standard error of the mean.
Fig 6.
Temperature response of (A) stomatal conductance [gs], (B) net photosynthesis [Pnet], (C) transpiration rate [E], and (D) leaf vapor pressure deficit [VPD leaf] in the field-grown im and TM-1 plants. Eighteen measurements were taken from the leaves located at 18th node of each NIL at three temperature points (30.42, 34.82, and 42.58°C, N = 6) with all other environmental variables constant.
Fig 7.
Variables of gas exchange and photosystem II function of the NIL leaves at the top canopy under locally applied high temperature treatment.
A. gs, stomatal conductance; B. E, transpiration rate; C. Pnet, net photosynthesis; D, Ci, intercellular CO2 concentration; E. Quantum yield; F. ETR, electron transport rate. * and ** above the bar indicate statistical significance between im and TM-1 at a given leaf temperature (p < 0.05 and 0.01), N = 6. Error bar represents standard error of the mean.
Fig 8.
Summary of leaf RNA-seq analysis comparing the NIL plants heat-stressed at 35°C.
A. Venn diagrams illustrating the up- and down-regulated genes in the im leaves. B. GO analysis of the up- and down-regulated genes in im leaves. The number of differentially expressed genes is shown in parenthesis and the color represents p values.
Table 2.
Annotation of differentially expressed genes and their relative degree of up- or down-regulation in the im leaves with reference to TM-1 from the plants incubated at 35°C for 3 days.
Fig 9.
Venn diagrams showing the numbers of commonly regulated genes in leaf and fiber tissues of the im plant.
Commonly up-regulated genes (URGs) and down-regulated genes (DRGs) were identified by comparing the DEGs determined from the NIL leaves (Fig 8) with the DEGs previously identified from developing NIL fibers at 28 DPA [24]. GO analyses identified temperature responses (GO:0009266) from the common 58 URGs and stress responses (GO:0006950) as well as the plant cell wall (GO:0009505) from the common 116 DRGs (S5 Table).