OsMPS, an R2R3-type MYB transcription factor of rice, is induced by salt stress and expressed in vegetative and reproductive tissues. In all, OsMPS is required for the adaptive growth response in rice during adverse environmental conditions.
1.OsMPS affects plant growth OsMPS is a direct regulator of genes encoding expansins, and it may function as a hub for multiple hormones to control plant growth. OsMPS overexpression plants were severely reduced in size under control conditions, and we find that seedlings overexpress ing OsMPS was significantly less affected by salt stress than in EV seedings.(Figure4) In a word,in the absence of stress, knockdown of OsMPS increased biomass accumulation, while OsMPS overexpression impaired growth.
2.OsMPS affects heading date and panicle-related traits OsMPS is expressed in anthers and spikelets, suggesting a role in reproductive development. OE6–2 plants showed a delay in heading and flowering by 21 days, and a reduced number of panicles per plant compared to the EV line.( Figure5) Down-regulation of OsMPScaused early heading and flowering.
3. OsMPS modulates the expression of hormone and cell wall-related genes OsMPS negatively regulates the expression of several ARF and IAA genes. Interestingly, the growth inhibition of OsMPS over-expression lines was partially rescued by low concentrations of exogenous auxin. OsMPS acts as a negative regulator of auxin related genes and cell wall-remodeling genes. BR biosynthesis and signaling genes were found to be down-regulated upon over-expression of OsMPS.
4.OsMPS affects the cell size and length of leaf epidermal cells
OsMPS is expressed in most tissues, including shoots, roots, anthers and seeds, but not in endosperm, stigma, ovary or the embryo. (Figure2') OsMPS is expressed in anthers and spikelets, suggesting a role in reproductive development. However, Over-expression of OsMPS resulted in decreased plant stature at the seedling, vegetative and heading stage.(Figure3')
After salt stress induction, OsMPS can express in 30 min and 1 h , and Up-regulation of OsMPS was also observed in leaves after salt stress.(Figure1') Moreover, OsMPS expression is modulated by multiple hormones, Auxin, BL and GA, which are known to promote cell elongation (Depuydt and Hardtke, 2011), transiently decrease the expression of OsMPS.
OsMPS is classified as an R2R3-type MYB TF belonging to clade C14, which includes AtMYB71, AtMYB79 and AtMYB121 from Arabidopsis and two uncharacterized rice MYB TFs. Using the web tool Phytozome (Goodsteinet al.,2012), homologous proteins from Sorghum bicolor, Zea mays and Setaria italica were identified and shown to share high sequence identity with OsMPS at the DNA-binding domain.
OsMPS mis-expression causes metabolic changes related to growth
In OsMPS overexpression plants, a low level of the tricarboxylic acid cycle intermediates 2–oxoglutarate, malate and fumarate was observed, and these intermediates are directly linked to plant development as their abundance is a potential growth signal. Metabolic profiling revealed that OsMPS over-expression results in accumulation of amino acids and decreased levels of tricarboxylic acid cycle intermediates, which may indicate a lower rate of protein synthesis and metabolism, correlating with the smaller plant size observed.
OsMPS contains a putative nuclear localization signal immediately downstream of the R2R3 domain, so it locates in the nucleus.
Labs working on this gene
Institute of Biochemistry and Biology, University of Potsdam, Karl Liebknecht Straße 24-25, Haus 20, 14476 Potsdam, Germany
Max Planck Institute of Molecular Plant Physiology, Am M€ uhlenberg 1, 14476 Potsdam, Germany
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