Morphogenesis of Stamens and Petaloid Stamens in Lilium hybrid ‘Red Twin’ under Different Temperatures and the Expression Characteristics of Two AGAMOUS-like Genes Linked to These Processes

Abstract

The double-flowered lily ‘Red Twin’, in which stamens are transformed into petaloid organs, sometimes exhibits normal stamens owing to an unknown mechanism and thus greatly affecting its commercial quality. In this study, the morphogenesis of stamens and petaloid stamens in this cultivar grown under different temperature treatments were investigated. Two AGAMOUS-like genes were isolated and their expression levels were analyzed. The results showed that relatively high temperatures induced the morphogenesis of stamens, while relatively low temperatures promoted petaloidy in ‘Red Twin’. The stage with 1–6 mm flower buds was identified as the critical development period for stamen morphogenesis; furthermore, keeping the flower buds under relatively low temperatures in the 1–3 or 3–6 mm stages would be sufficient for the formation of petaloid stamens to a high degree. In addition, LrtAG1 and LrtAG2 showed the highest expression level in whorls 3 and 4 of 3–6 mm flower buds, respectively. LrtAG1 showed a higher reduction ratio than LrtAG2 when the flower buds were transferred to low temperature, implying that the decreased LrtAG1 expression level is associated with low temperature and might be correlated with the petaloidy of the stamens.

Seasonal variation of two floral patterns in Clematis ‘Vyvyan Pennell’ and its underlying mechanism

“…Similarly, short-term high (35 ℃) or low (2 ℃) temperatures may cause high malformation rates of flowers in strawberry cultivars ‘Maehyang’ and ‘Seolhyang’ [ 63 ]. While in some other horticultural varieties, such as Lilium hybrid ‘Red twin’ [ 25 ], and Rosa chinensis ‘Old blush’ [ 26 ], the effect of temperature creates unique ornamental values of double-flower traits. Until now, the precise mechanism underlying the regulation of floral pattern changes by temperature remains elusive.…”

“…This upregulation may be attributed to the presence of three heat shock elements and one low-temperature response element on the gene promoter [ 26 ]. In the Lilium hybrid ‘Red twin’, LrtAG1 of the C-class gene might be correlated with the petaloidy of stamens, as it showed a higher reduction ratio when the floral buds were transferred to a low temperature [ 25 ].…”

“…Conversely, higher temperatures (ranging from 20 to 26 ℃) can facilitate the normal development of stamens. In the study of double-flowered Lilium hybrid ‘Red Twin’ [ 25 ], it was observed that the expression levels of LrtAG1 were reduced at relatively low temperatures, resulting in a narrower expression region and the development of petaloid stamens. Similarly, in Rosa chinensis ’ Old Blush’, the APETALA 2 ( AP2 ) gene was found to be a significant factor contributing to the formation of petaloid stamens under different temperature conditions [ 26 ].…”

Pedigree-based QTL analysis of flower size traits in two multi-parental diploid rose populations

“…A recent study suggested that the transcription factor RhMYB123 is involved in the development of petaloid stamens in roses (Li et al, 2022a). Moreover, a previous study reported that PD morphology was affected by temperatures indicating that low temperatures induced petaloid stamens in roses (Ma et al, 2015;Li et al, 2022b).…”

“…The phenomenon of petaloid stamens is more common in double flowers and caused by the mutation, downregulation, or expressional boundary shift of AGAMOUS homologs. Petaloid stamens have been reported in several species besides roses ( Galimba et al., 2012 ; Bendahmane et al., 2013 ; Liu et al., 2013 ; Noor et al., 2014 ; Sun et al., 2014 ; Ma et al., 2015 ; Mizunoe and Ozaki, 2015 ; Nakatsuka and Koishi, 2018 ; Li et al., 2022b ). A recent study suggested that the transcription factor RhMYB123 is involved in the development of petaloid stamens in roses ( Li et al., 2022a ).…”