Cytokinin-Auxin Crosstalk in the Gynoecial Primordium Ensures Correct Domain Patterning

Abstract

The Arabidopsis (Arabidopsis thaliana) gynoecium consists of two congenitally fused carpels made up of two lateral valve domains and two medial domains, which retain meristematic properties and later fuse to produce the female reproductive structures vital for fertilization. Polar auxin transport (PAT) is important for setting up distinct apical auxin signaling domains in the early floral meristem remnants allowing for lateral domain identity and outgrowth. Crosstalk between auxin and cytokinin plays an important role in the development of other meristematic tissues, but hormone interaction studies to date have focused on more accessible later-stage gynoecia and the spatiotemporal interactions pivotal for patterning of early gynoecium primordia remain unknown. Focusing on the earliest stages, we propose a cytokinin-auxin feedback model during early gynoecium patterning and hormone homeostasis. Our results suggest that cytokinin positively regulates auxin signaling in the incipient gynoecial primordium and strengthen the concept that cytokinin regulates auxin homeostasis during gynoecium development. Specifically, medial cytokinin promotes auxin biosynthesis components [YUCCA1/4 (YUC1/4)] in, and PINFORMED7 (PIN7)-mediated auxin efflux from, the medial domain. The resulting laterally focused auxin signaling triggers ARABIDOPSIS HISTIDINE PHOSPHOTRANSFER PROTEIN6 (AHP6), which then represses cytokinin signaling in a PAT-dependent feedback. Cytokinin also down-regulates PIN3, promoting auxin accumulation in the apex. The yuc1, yuc4, and ahp6 mutants are hypersensitive to exogenous cytokinin and 1-napthylphthalamic acid (NPA), highlighting their role in mediolateral gynoecium patterning. In summary, these mechanisms self-regulate cytokinin and auxin signaling domains, ensuring correct domain specification and gynoecium development.

Regulation of ovule initiation by gibberellins and brassinosteroids in tomato and Arabidopsis: two plant species, two molecular mechanisms

“…A key step in ovule development is determination of the position and number of ovule primordia in the CMM (Cucinotta et al , ). CMM and ovule primordia formation are both controlled by regulatory genes, as well as by several plant growth regulators, including auxin, cytokinin (CKs), and brassinosteroids (BRs) (Bartrina et al , ; Bencivenga et al , ; Huang et al , ; Galbiati et al , ; Reyes‐Olalde et al , ; Cucinotta et al , , ; Müller et al , ). Recently, we have demonstrated that gibberellins (GAs) also play an important role in modulation of ovule number in Arabidopsis as well as in tomato and rapeseed (Gomez et al , ).…”

Antagonistic activity of auxin and cytokinin in shoot and root organs

“…Auxin and cytokinin were shown to interact both antagonistically and synergistically during the development of root and shoot apical meristems and these interactions involve coordination of signaling, biosynthesis, and transport pathways to delineate stem cell niches, meristem growth, vascular pattern formation, and organ initiation in the shoot (Besnard et al., ; Bishopp et al., ; Chickarmane, Gordon, Tarr, Heisler, & Meyerowitz, ; Dello Ioio et al., ; Truskina & Vernoux, ). Auxin–cytokinin interactions have also been shown to be essential for the control of the development of determinate meristems such as those needed for gynoecium development (Muller, Larsson, Spichal, & Sundberg, ; Reyes‐Olalde et al., ).…”

Impact of Explants, Plant Growth Regulators and their Interaction on Micropropagation of Impatiens balsamina, L.

“…Which both of auxin and cytokinin are usually required for growth or morphogenesis. Auxin blocks cytokinin signaling (Müller et al, 2017) while cytokinins can inhibit at least some of the action of auxin. Cotyledonary node with section of cotyledon was subcultured or re-cultured in MS medium containing PGR according to treatments.…”