XAANTAL1 Reveals an Additional Level of Flowering Regulation in the Shoot Apical Meristem in Response to Light and Increased Temperature in Arabidopsis

Abstract

Light and photoperiod are environmental signals that regulate flowering transition. In plants like Arabidopsis thaliana, this regulation relies on CONSTANS, a transcription factor that is negatively posttranslational regulated by phytochrome B during the morning, while it is stabilized by PHYA and cryptochromes 1/2 at the end of daylight hours. CO induces the expression of FT, whose protein travels from the leaves to the apical meristem, where it binds to FD to regulate some flowering genes. Although PHYB delays flowering, we show that light and PHYB positively regulate XAANTAL1 and other flowering genes in the shoot apices. Also, the genetic data indicate that XAL1 and FD participate in the same signaling pathway in flowering promotion when plants are grown under a long-day photoperiod at 22 °C. By contrast, XAL1 functions independently of FD or PIF4 to induce flowering at higher temperatures (27 °C), even under long days. Furthermore, XAL1 directly binds to FD, SOC1, LFY, and AP1 promoters. Our findings lead us to propose that light and temperature influence the floral network at the meristem level in a partially independent way of the signaling generated from the leaves.

The origin and the genetic regulation of the self-compatibility mechanism in clementine (Citrus clementina Hort. ex Tan.)

“…AGAMOUS-LIKE 61 ( AGL61, CICLE_v10006615mg ) also termed DIANA or DIA , is a type I MADS box involved in embryo formation and seed growth, in Arabidopsis; loss of AGL61/DIA function impairs central cell maturation and shows decreased female fertility ( Bemer et al., 2008 ; Steffen et al., 2008 ). AGAMOUS-LIKE 12 ( AGL12, CICLE_v10023354mg ) also termed XAANTAL1 ( XAL1 ) encodes for a transcription factor that belong to type II Arabidopsis MADS-box genes; it is implicated in root development and flowering transition, in particular this gene participates in the photoperiod pathway ( Tapia-López et al., 2008 ; Rodríguez-Bolaños et al., 2023 ). The MLO -like protein 12 belongs to MLO genes that encode plasma membrane proteins with a calmodulin-binding domain essential for successful colonization of powdery mildew pathogens in numerous crops ( Devoto et al., 1999 ; Kim et al., 2002 ).…”

“…, 2 0 0 8 ) . AG A M O U S -L I K E 1 2 ( A G L 1 2 , CICLE_v10023354mg) also termed XAANTAL1 (XAL1) encodes for a transcription factor that belong to type II Arabidopsis MADS-box genes; it is implicated in root development and flowering transition, in particular this gene participates in the photoperiod pathway (Tapia-Loṕez et al, 2008;Rodrıǵuez-Bolaños et al, 2023). The MLO-like protein 12 belongs to MLO genes that encode plasma membrane proteins with a calmodulin-binding domain essential for successful colonization of powdery mildew pathogens in numerous crops (Devoto et al, 1999;Kim et al, 2002).…”

Functional Overview on Mads Box: A Meta-Review

“…AP1 and its clade members (including FUL) function terminally in the flowering pathway, and XAL1 mainly contributes to root growth and development as well as in flowering process. While its defect brings significant delay in the process, its overexpression effect on flowering is not as significant likely because XAL1 itself may not be sufficient to activate its target genes involved in the process [55,135].…”