The MADS Box Genes ABS, SHP1, and SHP2 Are Essential for the Coordination of Cell Divisions in Ovule and Seed Coat Development and for Endosperm Formation in Arabidopsis thaliana

Abstract

Seed formation is a pivotal process in plant reproduction and dispersal. It begins with megagametophyte development in the ovule, followed by fertilization and subsequently coordinated development of embryo, endosperm, and maternal seed coat. Two closely related MADS-box genes, SHATTERPROOF 1 and 2 (SHP1 and SHP2) are involved in specifying ovule integument identity in Arabidopsis thaliana. The MADS box gene ARABIDOPSIS BSISTER (ABS or TT16) is required, together with SEEDSTICK (STK) for the formation of endothelium, part of the seed coat and innermost tissue layer formed by the maternal plant. Little is known about the genetic interaction of SHP1 and SHP2 with ABS and the coordination of endosperm and seed coat development. In this work, mutant and expression analysis shed light on this aspect of concerted development. Triple tt16 shp1 shp2 mutants produce malformed seedlings, seed coat formation defects, fewer seeds, and mucilage reduction. While shp1 shp2 mutants fail to coordinate the timely development of ovules, tt16 mutants show less peripheral endosperm after fertilization. Failure in coordinated division of the innermost integument layer in early ovule stages leads to inner seed coat defects in tt16 and tt16 shp1 shp2 triple mutant seeds. An antagonistic action of ABS and SHP1/SHP2 is observed in inner seed coat layer formation. Expression analysis also indicates that ABS represses SHP1, SHP2, and FRUITFUL expression. Our work shows that the evolutionary conserved Bsister genes are required not only for endothelium but also for endosperm development and genetically interact with SHP1 and SHP2 in a partially antagonistic manner.

Identification, Characterization and Functional Analysis of C-Class Genes Associated with Double Flower Trait in Carnation (Dianthus caryphyllus L.)

“…In Arabidopsis, AG is one of the key genes for double flower formation. SHP was not physically present in the meristem or primordia cells at the investigated time, indicating that AG is the only C function factor in the process of floral primordia development [34,35]. The change in expression pattern is reported to lead to subfunctionalization of C function genes [36,37].…”

A link between LEAFY and B‐gene homologues in Welwitschia mirabilis sheds light on ancestral mechanisms prefiguring floral development

“…This result is consistent with observations made in angiosperms. For example, in Arabidopsis, the Bsister gene TRANSPARENT TESTA16/ ARABIDOPSIS BSISTER (TT16/ABS) is involved in seed coat pigmentation (Nesi et al, 2002), outer integument development (De Folter et al, 2006;Prasad et al, 2010) and also participates in endosperm development (Ehlers et al, 2016). This led to the conclusion that, in angiosperms and perhaps in gymnosperms, Bsister genes are not essential for specifying female organ identity, but may contribute to the development of fertile ovules and seeds (reviewed in Bernardi et al, 2014).…”

Unraveling the transcriptional complexity of compactness in sistan grape cluster

“…The two SHP1 and SHP2 genes contain MADS-box domain. They works for ovarian shell specific differentiation so that mutation leads to defection in seeds shell and reduction in seed number and mucilage [39].…”