AUTHOR=Rahim Md Abdur , Resentini Francesca , Dalla Vecchia Francesca , Trainotti Livio 

TITLE=Effects on Plant Growth and Reproduction of a Peach R2R3-MYB Transcription Factor Overexpressed in Tobacco

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 10 - 2019

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.01143

DOI=10.3389/fpls.2019.01143

ISSN=1664-462X

ABSTRACT=In plants, anthocyanin production is controlled by MYB and bHLH transcription factors. In peach, among the members of these families, MYB10.1 and bHLH3 have been shown to be the most important genes for production of these pigments during fruit ripening. Anthocyanins are valuable molecules and the over-expression of regulatory genes in annual fast growing plants have been explored for their biotechnological production.
The over-expression of peach MYB10.1 in tobacco plants induced anthocyanin pigmentation which was particularly strong in the reproductive parts. Pigments production was the result of an up-regulation of the expression level of key genes of the flavonoid biosynthetic pathway, such as NtCHS, NtCHI, NtF3H, NtDFR, NtANS and NtUFGT as well as of the proanthocyanindin biosynthetic pathway like NtLAR. Nevertheless, phenotypic alteration in transgenic tobacco lines were not only limited to anthocyanins production. Lines showing a strong phenotype (Type-I) exhibited irregular leaf shape and size and reduced plant height. Moreover, flowers had reduced length of anther’s filament, non-dehiscent anthers, reduced pistil length, aborted nectary glands and impaired capsule development but reproductive parts including androecium, gynoecium and petals were more pigmented that in WT. Surprisingly, over-expression of peach MYB10.1 led to suppression of NtMYB305, which is required for floral development, and of one of its target genes, NECTARIN1 (NtNCE1), involved in the nectary gland formation.
MYB10.1 over-expression up-regulated JA biosynthetic (NtAOS) and signaling (NtJAZd) genes, as well as 1-AMINOCYCLOPROPANE-1-CARBOXYLATE OXIDASE (NtACO) in flowers. The alteration of these hormonal pathways might be among the causes of the observed floral abnormalities with defects in both male and female gametophyte development. In particular, only about 30% of pollen grains of Type-I lines were viable while during megaspore formation there was a block during FG1 (St3-II). This block seemed to be associated to an excessive accumulation of callose.
It can be concluded that the over-expression of peach MYB10.1 in tobacco not only regulates flavonoid biosynthesis (anthocyanin and proanthocyanidin) in the reproductive parts but also plays a role in other processes like vegetative and reproductive development.