ABSTRACT
MDN1/Rea1, as an AAA-type ATPase, is predicted to be the largest protein involved in pre-ribosome maturation in most organisms. However, its function in plant growth and development is poorly understood. Here, we characterized a novel Arabidopsis mutant, dwarf &short root (dsr) 1, which shows pleiotropic developmental phenotypes, such as slow germination, short root, dwarf shoot, and reduced seed set under normal growth conditions. Using positional cloning, we revealed that the AtMDN1 function is impaired by a 'glutamic acid' to 'lysine' change at position 3838 of the amino acid sequence in dsr1. Multiple sequence alignment analysis revealed that the mutated Glu residue, which located in the linker domain of AtMDN1, is extremely conserved among organisms. AtMDN1 is expressed in various tissues, particularly in the shoot apex and root tip. Moreover, the results of transcript profile analyses showed that the dysfunction of AtMDN1 in dsr1 impairs the expression of genes related to plant growth and development, which is tightly associated with the pleiotropic phenotypes of dsr1. Thus, we concluded that the Glu residue plays a vital role in maintaining AtMDN1 functions, which are essential for plant growth and development.
Subject(s)
ATPases Associated with Diverse Cellular Activities/metabolism , Arabidopsis Proteins/metabolism , Arabidopsis/genetics , ATPases Associated with Diverse Cellular Activities/chemistry , ATPases Associated with Diverse Cellular Activities/genetics , Amino Acid Sequence , Arabidopsis/metabolism , Arabidopsis Proteins/chemistry , Arabidopsis Proteins/genetics , Germination , Mutagenesis, Site-Directed , Phenotype , Plant Roots/metabolism , Plant Shoots/metabolism , Plants, Genetically Modified/genetics , Plants, Genetically Modified/growth & development , Plants, Genetically Modified/metabolism , RNA, Plant/chemistry , RNA, Plant/isolation & purification , RNA, Plant/metabolism , Sequence Alignment , Sequence Analysis, RNA , TranscriptomeABSTRACT
The chloroplast-localized proteins play roles in plant salt stress response, but their mechanisms remain largely unknown. In this study, we screened a yellow leaf mutant, yl1-1, whose shoots exhibited hypersensitivity to salt stress. We mapped YL1 to AT3G57180, which encodes a YqeH-type GTPase. YL1, as a chloroplast stroma-localized protein, could be markedly reduced by high salinity. Upon exposure to high salinity, seedling shoots of yl1-1 and yl1-2 accumulated significantly higher levels of Na(+) than wild type. Expression analysis of factors involved in plant salt stress response showed that the expression of ABI4 was increased and HKT1 was evidently suppressed in mutant shoots compared with the wild type under normal growth conditions. Moreover, salinity effects on ABI4 and HKT1 were clearly weakened in the mutant shoots, suggesting that the loss of YL1 function impairs ABI4 and HKT1 expression. Notably, the shoots of yl1-2 abi4 double mutant exhibited stronger resistance to salt stress and accumulated less Na(+) levels after salt treatment compared with the yl1-2 single mutant, suggesting the salt-sensitive phenotype of yl1-2 seedlings could be rescued via loss of ABI4 function. These results reveal that YL1 is involved in the salt stress response of seedling shoots through ABI4.
ABSTRACT
Volatile esters are major factors affecting the aroma of apple fruits, and alcohol acyltransferases (AATs) are key enzymes involved in the last steps of ester biosynthesis. The expression of apple AAT (MdAAT2) is known to be induced by salicylic acid (SA) or ethylene in apple fruits, although the mechanism of its transcriptional regulation remains elusive. In this study, we reveal that two apple transcription factors (TFs), MdMYB1 and MdMYB6, are involved in MdAAT2 promoter response to SA and ethylene in transgenic tobacco. According to electrophoretic mobility shift assays, MdMYB1 or MdMYB6 can directly bind in vitro to MYB binding sites in the MdAAT2 promoter. In vivo, overexpression of the two MYB TFs can greatly enhance MdAAT2 promoter activity, as demonstrated by dual luciferase reporter assays in transgenic tobacco. In contrast to the promoter of MdMYB1 or MdMYB6, the MdAAT2 promoter cannot be induced by SA or ethephon (ETH) in transgenic tobacco, even in stigmas in which the MdAAT2 promoter can be highly induced under normal conditions. However, the induced MYB TFs can dramatically enhance MdAAT2 promoter activity under SA or ETH treatment. We conclude that MdMYB1 and MdMYB6 function in MdAAT2 responses to SA and ethylene in transgenic tobacco, suggesting that a similar regulation mechanism may exist in apple.
