Leaf Coloration in Acer palmatum Is Associated with a Positive Regulator ApMYB1 with Potential for Breeding Color-Leafed Plants.

Anthocyanin biosynthesis and accumulation is closely associated with tissue/organ coloring in plants. To gain insight into the physiological and molecular mechanisms of leaf coloring in Acer palmatum, a deciduous tree during autumnal senescence, we first investigated concentration dynamics of pigments (i.e., chlorophyll, carotenoid and anthocyanin) in leaves with differential coloring. It was found that compared to green leaves (GN), anthocyanins were accumulated actively in semi-red (SR) and total-red (TR) leaves, accompanied with chlorophyll and carotenoid degradation. Then transcriptional profiling on GN and SR leaves identified thousands of transcripts with differential expression in SR compared to GN leaves. An annotation search showed that the entire flavonoid/anthocyanin biosynthesis pathway from the production of naringenin chalcone to modification of flavonoid backbone was extensively activated at the transcriptional level in SR leaves. Phylogenetic analysis of putative MYB proteins identified ApMYB1 as a putative regulator promoting anthocyanin biosynthesis. Expression of ApMYB1 in leaves was induced by exogenous hormones including abscisic acid. Stable overexpression of ApMYB1 in tobacco resulted in leaves with higher accumulation of anthocyanins. Collectively, our results identified ApMYB1 as a positive regulator associated with leaf coloring in Acer palmatum during autumnal senescence, which may be regarded a potential target for breeding color-leafed plants.

Identification of a MYB3R gene involved in drought, salt and cold stress in wheat (Triticum aestivum L.).

Abiotic stress seriously affects crop growth and productivity. To better understand the mechanisms plant uses to cope with drought, cold and salt stress, it is necessary to isolate and characterize important regulators response to these stresses. In this study, we cloned a MYB gene from wheat (Triticum aestivum L.) and designated it as TaMYB3R1 based on its conserved three repeats in MYB domain. The sequence of TaMYB3R1 protein shares high identity to other plant MYB3R proteins. Subcellular localization experiment in onion epidermal cells proved that TaMYB3R1 localized in the nucleus. Trans-activation essays in yeast cells confirmed that TaMYB3R1 was a transcriptional activator, and only C-terminal region was able to activate the expression of ß-galactosidase. DNA-binding test showed the MSA cis element-binding activity of TaMYB3R1. After exogenous application of phytohormone ABA, the expression of TaMYB3R1 was induced, and its transcripts accumulated up to 24h; this is also the case for MeJA treatment, but after it peaked at 4h, it decreased to low levels. However, either SA or ET had no obvious effect on the expression of TaMYB3R1. Furthermore, the TaMYB3R1 was initially expressed at low levels and was gradually induced following treatment with salt, and continued to increase up to 72 h. This was similar for the cold treatment. In contrast, the peak appeared at 6h of the PEG treatment, and then gradually decreased to low levels. Our results suggest that TaMYB3R1 is potentially involved in wheat response to drought, salt and cold stress.