Effect of <i>Ppd-1</i> on the expression of flowering-time genes in vegetative and reproductive growth stages of wheat

Abstract

The photoperiod sensitivity gene Ppd-1 influences the timing of flowering in temperate cereals such as wheat and barley. The effect of Ppd-1 on the expression of flowering-time genes was assessed by examining the expression levels of the vernalization genes VRN1 and VRN3/WFT and of two CONSTANS-like genes, WCO1 and TaHd1, during vegetative and reproductive growth stages. Two nearisogenic lines (NILs) were used: the first carried a photoperiod-insensitive allele of Ppd-1 (Ppd-1a-NIL), the other, a photoperiod-sensitive allele (Ppd-1b-NIL). We found that the expression pattern of VRN1 was similar in Ppd-1a-NIL and Ppd1b-NIL plants, suggesting that VRN1 is not regulated by Ppd-1. Under long day conditions, VRN3/WFT showed similar expression patterns in Ppd-1a-NIL and Ppd-1b-NIL plants. However, expression differed greatly under short day conditions: VRN3/WFT expression was detected in Ppd-1a-NIL plants at the 5-leaf stage when they transited from vegetative to reproductive growth; very low expression was present in Ppd-1b-NIL throughout all growth stages. Thus, the Ppd-1b allele acts to down-regulate VRN3/WFT under short day conditions. WCO1 showed high levels of expression at the vegetative stage, which decreased during the phase transition and reproductive growth stages in both Ppd-1a-NIL and Ppd-1b-NIL plants under short day conditions. By contrast to WCO1, TaHd1 was up-regulated during the reproductive stage. The level of TaHd1 expression was much higher in Ppd-1a-NIL than the Ppd-1b-NIL plants, suggesting that the Ppd-1b allele down-regulates TaHd1 under short day conditions. The present study indicates that down-regulation of VRN3/WFT together with TaHd1 is the cause of late flowering in the Ppd-1b-NIL plants under short day conditions.

A wheat homologue of <i>PHYTOCLOCK 1</i> is a candidate gene conferring the early heading phenotype to einkorn wheat

“…CO proteins are degraded in the dark and function only during light periods (Valverde et al, 2004). Moreover, TaHd1 activates WFT under SD conditions in wheat, unlike WCO1 (Kitagawa et al, 2012). Therefore, abundantly accumulated TaHd1 transcripts during day may promote WFT expression under SD conditions in the early mutant.…”

Winter Memory throughout the Plant Kingdom: Different Paths to Flowering

“…The photoperiodic activation of FT involves the PRR PHOTOPERIOD1 (PPD1), which is responsible for a large part of the natural variation in flowering observed in wheat and barley; varieties with active PPD1 contain high levels of FT and flower early, whereas ppd1 varieties have low FT and flower late (Turner et al, 2005;Beales et al, 2007;Kitagawa et al, 2012;Shaw et al, 2012). How PPD1 controls FT expression in grasses is not known, but it possibly acts through the transcriptional regulation of CONSTANS (Turner et al, 2005;Shaw et al, 2012).…”

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“…For example, stress could stimulate blossom that has been found correlating to CO-like (COL) gene (Higgins et al, 2010;Kikuchi et al, 2012;Kitagawa et al, 2012). Treatment with ultrasound stress could stimulate bacterial growth (Pitt and Ross, 2003).…”