## 3 Discussion
For different plant tissues, IPG strips of different pH ranges were used to ensure that the pIs of the most proteins were covered and to prevent the clustering of proteins with similar pIs [24]. In general, for the separation of proteins from plant tissues, IPG strips of pH 4-7 were used because such strips can resolve more than 80% of the protein spots in a gel [25]. The Rubisco large subunit (Spot #1011) catalyzes the first step of CO2 assimilation and photorespiration [26]. Rubisco activity limits photosynthesis in C3 plants [27; 28]. This enzyme was up-regulated in tall mutants, indicating that tall mutants can maintain a high efficiency of photosynthesis compared to the control. Increased photosynthesis enhances crop yields [29; 30]. Therewas down-regulation of this enzyme in dwarf mutants when compared to the control. Ribulose bisphosphate carboxylase/oxygenase activase (Spot #3401) mediates the activation of Rubisco by facilitating the ATP-dependent removal of various inhibitory sugar phosphates from the Rubisco's active site [31]. Reduced expression of Rubisco activase has been reported to decrease photosynthesis and growth rates [31]. This spot was down regulated in dwarf mutants and up-regulated in tall mutants. The down-regulation of Rubisco activase revealed that the photosynthetic apparatus undergoes extensive degradation [32], leading to a low photosynthetic rate. Overexpression of Rubisco and Rubisco activase in tall mutants indicated that these mutants increased the capacity of photosynthetic flux and biomass production compared to the other mutants and the control, thereby presenting good growth and seed yields. The Oxygen evolving enhancer protein (spot #1201) is a subunit of the oxygen-evolving complex of photosystem II in the chloroplast [33]. It stabilizes the PSII and, thus, has an important role in the primary reaction of photosynthesis. Up-regulation of this protein was observed in tall mutants. No effect on the intensity of this protein was found in the semi-dwarf mutant. It is suggested that oxygen-evolving complex proteins help the tall mutant plants adapt to adverse conditions, thereby releasing the oxygen-evolving enhancer protein. The gamma chain of ATP synthase (spot #4201) is involved in ATP biosynthetic pathway, producing ATP from ADP, and takes part in photophosphorylation [34]. In our study, this protein was up-regulated in both tall and semi-dwarf mutants. The expression of this protein was equal to that of the control in dwarf mutants. An earlier study at the transcript level showed the decreased expression of ATP synthase gamma chain under stress condition [35]. The Chloroplastic PSII stability/assembly factor HCF 136 (spot #4301) stabilizes and activates the PSII complex [36; 37]. Overexpression of this protein in tall mutants, therefore, indicates activated PSII and efficient photosynthesis compared to the control and the other mutant lines. The GAPDH takes part in glycolysis, an important metabolic pathway providing energy and maintaining production of both primary and secondary metabolites [38]. It was up-regulated in tall and semi-dwarf mutants. The TCA cycle is a fundamental metabolic pathway, the intermediates of which form important metabolites and substrates for amino-acid synthesis. Malate dehydrogenase (spot #2101), an important enzyme of the TCA cycle, did not show any change in the expression of tall mutants compared to the control and was up-regulated in other mutant plants. Sucrose phosphate synthase (spot #4601) regulates the balance between starch and sucrose. It is involved in sucrose degradation, as well as sucrose synthesis [39]. This enzyme was up-regulated in tall mutants, possibly to meet energy demands. Deoxyuridine 5'-triphosphate nucleotide hydrolase (spot #3001) decreases the level of dUTP so that uracil cannot be incorporated into DNA. Down-regulation of this gene under stress conditions resulted in damaging the DNA [40].