Flowering plants form the largest group of plants. Within this group, there was a great evolutionary progress, as so-called juice fruits emerged. Where seeds of dried fruit previously spread out only by mechanical ejection, wind or contact with animals, now the radius of the spread increased significantly: animals that digested the fruits, after some time excreted the undigested seeds - and then often much farther away. This reduces competition between parent plants and their offspring and improves the reproductive and distributional success of the juice fruit crops.
Central to this is the regulation of ripening for the juice crops. In spite of independent evolution, various climacteric (juxtaposed) fruits now have the plant hormone ethylene as a ripening signal. It triggers the process that changes color, texture, taste and the nutritional value of the fruit. In too large quantities, however, ethylene causes the fruit to decay. An international research team has now discovered how plants control the synthesis of ethylene and the signals associated with maturation.
Comprehensive database through "fruitENCODE"
Researchers from Silin Zhong of the Chinese University of Hong Kong used the data from the "fruitENCODE" project, which, similar to the human "ENCODE" project, analyzes not only genes but the DNA information. These include gene expression, DNA methylation, changes in histones, accessibility of chromatin regions, and binding sites for the interaction of proteins with DNA.
In total, the data comprise 361 transcriptomes, 71 chromatin, 147 histone and 45 DNA methylation profiles obtained by various sequencing methods (whole genome bisulfite sequencing, ChIP-Seq, DNase I-Seq and RNA-Seq).
In the data, the scientists discovered three different transcriptional regulatory circuits for fruit ripening in climacteric juice crops:
1. Eudicotyledons such as tomato, apple and pear, which have undergone genome duplication in their evolution, utilize the duplicated MADS transcription factors.
2. Species without genome duplication, such as peach, papaya and melon, use the NAC transcription factors that are actually relevant for senescence.
3. A third case is formed by the monocotyledonous banana, which is doubled in its genome and which binds both regulatory circuits together.
Furthermore, it turned out that the genes involved and their epigenetic regulation also exist in non-climacteric and even dried fruits. This suggests a common origin in regulatory processes, with different functions in evolutionarily older flowering plants.
Source: Pflanzenforschung.de
