Abstract:As one of the important mechanisms of epigenetic regulation， usually occurs in plant cytosine bases， including CG， CHG and CHH. DNA methylation mainly affects chromatin structure and gene transcription level. DNA methylation plays important roles in transcriptional regulation and maintaining the genome stability. Abiotic stresses affect plant growth and reproduction and ultimately lead to plant death. Based on existing research findings， DNA methylation can induce phenotypic alterations in plants under stress.To cope with abiotic stresses， the change mechanism of DNA methylation level during growth is affected by methylase and demethylase. The signal transduction pathways can change the expression of some stress response genes， thus causing changes in plant morphology， physiology and biochemistry to adapt to adversity. Some genes are upregulated （initiate） or downregulated （close down） in expression in order to assure the adaptive growth and development of plant， thus enabling plants to adapt and resist stress damage to a certain extent. This article reviews the DNA methylation modification and its role in transcriptional regulation， research progress in the growth and development of horticultural plants， and the epigenetic regulation of abiotic stress as well as the problems and prospective of horticultural plants. It provides a reference for the genetic improvement of horticultural plants and deciphering the mechanism of stress resistance.

Abstract:Carrot (Daucus carota L.), which is one of the top-ten ranking vegetable crops in the world, is an important source of vitamin A in human diets. China is a major producer of carrot and has rich carrot landraces with colors (i.e. orange, red, yellow and purple). The carrot germplasm resources with diverse root colors enabled deciphering the regulation mechanisms of the synthesis and metabolism of carotenoids and anthocyanins, and the origin and domestication of carrot. This article outlined the domestication history and major pigment components of carrot with different root colors, reviewed the research progress of genetic loci and functional genes modulating the accumulation of carotenoids and anthocyanins in carrot roots, introduced the uses and breeding methods of varieties with different root colors, as well as provided prospects in future research of carrot root color traits, thus serving as a basis for understanding the regulation mechanisms of carrot root color and breeding with colorful varieties.

Abstract:Seed germination and dormancy are two complicated and closely related physiological processes involving a series of interactions between external environment conditions and internal factors, which are of great significance to high and stable yield and ecological evolution. These traits are typically controlled by multiple loci and largely influenced by environmental factors. In recent years, several QTL involving in seed germination and dormancy have been identified and their functional mechanisms have been investigated. In this paper, the effects of genetic regulation and external factors on seed germination and dormancy were reviewed, the existing problems were summarized, and the future development areas were prospected.