An integrative model of the control of ovule primordia formation

Abstract

SUMMARYUpon hormonal signaling, ovules develop as lateral organs from the placenta. Ovule numbers ultimately determine the number of seeds that develop, and thereby contribute to the final seed yield in crop plants. We demonstrate here that CUP-SHAPED COTYLEDON 1 (CUC1), CUC2 and AINTEGUMENTA (ANT) have additive effects on ovule primordia formation. We show that expression of the CUC1 and CUC2 genes is required to redundantly regulate expression of PINFORMED1 (PIN1), which in turn is required for ovule primordia formation. Furthermore, our results suggest that the auxin response factor MONOPTEROS (MP/ARF5) may directly bind ANT, CUC1 and CUC2 and promote their transcription. Based on our findings, we propose an integrative model to describe the molecular mechanisms of the early stages of ovule development.

Cytokinin response factors integrate auxin and cytokinin pathways for female reproductive organ development

“…Indeed, mutants that have a reduced capacity for CK production or perception exhibit a dramatic reduction in ovule number and pistil size, and compromised female fertility (Kinoshita-Tsujimura and Kakimoto, 2011;Riefler et al, 2006;Werner et al, 2003). By contrast, increased CK levels result in a bigger pistil with a greater number of ovules compared with wild type, confirming a positive correlation between CK levels and ovule numbers (Bartrina et al, 2011;Bencivenga et al, 2012;Galbiati et al, 2013). It has been shown that CK treatment positively influences the number of ovules per pistil via a strong increase in PIN1 expression (Bencivenga et al, 2012;Galbiati et al, 2013;Zúñiga-Mayo et al, 2014).…”

“…By contrast, increased CK levels result in a bigger pistil with a greater number of ovules compared with wild type, confirming a positive correlation between CK levels and ovule numbers (Bartrina et al, 2011;Bencivenga et al, 2012;Galbiati et al, 2013). It has been shown that CK treatment positively influences the number of ovules per pistil via a strong increase in PIN1 expression (Bencivenga et al, 2012;Galbiati et al, 2013;Zúñiga-Mayo et al, 2014).…”

“…In the placenta, CKs promote PIN1 expression , which is needed for the establishment of the auxin gradient that leads to ovule primordia development (Bencivenga et al, 2012;Benková et al, 2003;Ceccato et al, 2013;Galbiati et al, 2013). Recently, it has been shown that three members of the CRF family, CRF2, CRF3 and CRF6, directly regulate PIN1 expression upon CK signalling in roots (Šimášková et al, 2015).…”

Effect of Constitutive miR164 Expression on Plant Morphology and Fruit Development in Arabidopsis and Tomato

“…The NAM/miR164 module is involved in leaf, carpel, and ovule development in model angiosperms [29,31,37,51,52]. In a previous study in the fruit of the prickly pear cactus, we found that miR164 is present in all developmental stages, and the temporal expression suggests that miR164 has different functions during fruit development of prickly pear fruit [46].…”

Molecular basis of fruit development

“…Cucinotta et al (2014) reviewed the early ovule development with a focus on the formation of the CMM and the initiation of ovule primordia in Arabidopsis. They presented a model of ovule initiation that relates the functions of CUC and ANT genes as well as the action of auxin, cytokinin, and brassinosteroid hormones (Galbiati et al, 2013;Cucinotta et al, 2014). Their model posits a role for ANT in the growth of the organ primordia, and CUC genes in the specification of the boundary zones between ovules.…”