The MYB family of transcription factors is important in regulatory networks controlling development, metabolism and responses to biotic and abiotic stresses in Arabidopsis. However, their role in regulating fatty acid accumulation in seeds is still largely unclear. Here, we found that MYB76, localized in the nucleus, was predominantly expressed in developing seeds during maturation. The myb76 mutation caused a significant increase in the amounts of total fatty acids and several major fatty acid compositions in mature seeds, suggesting that MYB76 functioned as an important repressor during seed oil biosynthesis. RNA sequencing and quantitative real-time PCR analysis revealed remarkable alteration of numerous genes involved in photosynthesis, fatty acid biosynthesis, modification, and degradation, and oil body formation in myb76 seeds at 12 days after pollination. These results help us to understand the novel function of MYB76 and provide new insights into the regulatory network of MYB transcriptional factors controlling seed oil accumulation in Arabidopsis.
Background
Plant Trihelix transcription factors, specifically bind to GT elements and play important roles in plant physiology and development. Wheat is a main cereal crop.
Brachypodium distachyon
is a close relative of wheat and has been described as a new model species for studying of grass functional genomics. Presently, little is known about wheat and
B. distachyon Trihelix
genes.
Results
In 51 species, 2387
Trihelix
genes were identified, including 80 wheat
Trihelix
genes and 27
B. distachyon Trihelix
genes. Consistent with the results of previous studies, these genes were classified into five subfamilies: GT-1, GT-2, SIP1, GTγ, and SH4. Members of the same subfamily shared similar gene structures and common motifs. Most
TaGT
and
BdGT
genes contained many kinds of
cis
-elements, such as development-, stress-, and phytohormone-related
cis
-acting elements. Additionally, 21 randomly selected
TaGT
genes were mainly expressed in the roots and flowers, while the expression of 19 selected
BdGT
genes was constitutive. These results indicate that the roles of
Trihelix
genes in wheat and
B. distachyon
might have diversified during the evolutionary process. The expression of the most selected
TaG
T and
BdGT
genes was down-regulated when exposed to low temperatures, NaCl, ABA, and PEG, implying that
TaGT
and
BdGT
genes negatively respond to abiotic stress. On the contrary, the expression of some genes was up-regulated under heat stress.
Conclusions
Trihelix
genes exist extensively in plants and have many functions. During the evolutionary process, this gene family expanded and their functions diversified. As a result, the expression pattern and functions of members of the same family might be different. This study lays a foundation for further functional analyses of
TaGT
and
BdGT
genes.
Electronic supplementary material
The online version of this article (10.1186/s12864-019-5494-7) contains supplementary material, which is available to authorized users.
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