SUPERMAN regulates floral whorl boundaries through control of auxin biosynthesis

Abstract

Proper floral patterning, including the number and position of floral organs in most plant species, is tightly controlled by the precise regulation of the persistence and size of floral meristems (FMs). In , two known feedback pathways, one composed of WUSCHEL (WUS) and CLAVATA3 (CLV3) and the other composed of AGAMOUS (AG) and WUS, spatially and temporally control floral stem cells, respectively. However, mounting evidence suggests that other factors, including phytohormones, are also involved in floral meristem regulation. Here, we show that the boundary gene () bridges floral organogenesis and floral meristem determinacy in another pathway that involves auxin signaling. SUP interacts with components of polycomb repressive complex 2 (PRC2) and fine-tunes local auxin signaling by negatively regulating the expression of the auxin biosynthesis genes (). In mutants, derepressed local activity elevates auxin levels at the boundary between whorls 3 and 4, which leads to an increase in the number and the prolonged maintenance of floral stem cells, and consequently an increase in the number of reproductive organs. Our work presents a new floral meristem regulatory mechanism, in which , a boundary gene, coordinates floral organogenesis and floral meristem size through fine-tuning auxin biosynthesis.

Comprehensive characterization of a floral mutant reveals the mechanism of hooked petal morphogenesis in Chrysanthemum morifolium

“…The observations suggest that the products of CUC homologs regulate petal fusion in chrysanthemum as they do in other plant species. SUPERMAN ( SUP ) maintains floral whorl boundaries by regulating auxin biosynthesis, and mutation of SUP leads to extra stamens in the position of the carpel (Sakai et al ., ; Xu et al ., ). Genes encoding homologs of SUP , involved in stamen and carpel development, were up‐regulated at S10 and SEB stages in ‘ADG’ (Figure c), suggesting that SUP may evolve a new function in ray petal development of chrysanthemum.…”

“…Furthermore, the expression levels of CUC3 homologs were also higher in another two hooked petal cultivars than in another two fused straight petal cultivars at SEB stage (Figure 8). The observations suggest that the products of CUC homologs regulate petal fusion in chrysanthemum as they do in (a) (Sakai et al, 1995;Xu et al, 2018). Genes encoding homologs of SUP, involved in stamen and carpel development, were upregulated at S10 and SEB stages in 'ADG' (Figure 7c), suggesting that SUP may evolve a new function in ray petal development of chrysanthemum.…”

“…Similarly, the tomato (Lycopersicon esculentum) CUC homolog GOBLET (GOB) specifies the leaflets' boundary and influences both leaf and petal development (Berger et al, 2009). SUPERMAN (SUP) maintains floral whorl boundaries by regulating auxin biosynthesis, and the loss-of-function mutation of SUP leads to extra stamens in the position of carpel (Sakai et al, 1995;Xu et al, 2018).…”

Gene Expression Profiling of the Shoot Meristematic Tissues in Woodland Strawberry Fragaria vesca

“…In addition, FvCLAVATA1, 2, 3 are abundantly expressed in all three tissue samples, consistent with their roles in Arabidopsis meristems (Supplementary Data 4). The REM in this study was obtained from flowers at stages 6-7, when expression levels of WUS, CLV1, and CLV3 start to decline in Arabidopsis FM (Clark et al, 1997;Schoof et al, 2000;Xu et al, 2018). Therefore, the abundant expression of these genes in strawberry REM may suggest that the strawberry REM needs to maintain its meristematic activity for an extended period of time to ensure continued enlargement of the receptacle leading to the production of more carpels.…”

Meristem Termination and Organ Number Control in Early Stage of Arabidopsis Flower Development

“…We recently showed that the Arabidopsis boundary gene SUPERMAN (SUP) controls the FM activity by finely tuning of local auxin biosynthesis [16]. The increased organ number in sup mutants suggests that SUP is involved in both floral patterning and FM determinacy [17,18].…”