Ppd-H1integrates drought stress signals to control spike development and flowering time in barley

Abstract

Highlight 19 We show that Ppd-H1 integrates photoperiod and drought stress signals via 20 FLOWERING LOCUS T 1 (FT1) and the downstream MADS-box genes BM3 and BM8 21 to modulate reproductive development, and shoot and spike morphology in barley. 22Abstract 23 Drought impairs growth and spike development and is therefore a major cause of yield 24 losses in the temperate cereals barley and wheat. Here, we show that the photoperiod 25 response gene PHOTOPERIOD-H1 (Ppd-H1) interacts with drought stress signals to 26 modulate spike development. We tested the effects of a continuous mild and a transient 27 severe drought stress on developmental timing and spike development in spring barley 28 cultivars with a natural mutation in ppd-H1 and derived introgression lines carrying the 29 wild-type Ppd-H1 allele from wild barley. Mild drought reduced the spikelet number and 30 delayed floral development in spring cultivars but not the introgression lines with a wild-31 type Ppd-H1 allele. Similarly, drought-triggered reductions in plant height, tiller and 32 spike number were more pronounced in the parental lines compared to the 33 introgression lines. Transient severe stress halted growth and floral development, upon 34 rewatering introgression lines, but not the spring cultivars, accelerated development so 35 that control and stressed plants flowered almost simultaneously. These genetic 36 differences in development were correlated with a differential downregulation of the 37 flowering promotors FLOWERING LOCUS T1 and the BARLEY MADS-box genes 38 BM3 and BM8. Our findings, therefore, demonstrate that Ppd-H1 affects 39 developmental plasticity in response to drought in barley. 40 41

Agronomic performance and flowering behavior in response to photoperiod and vernalization in barley (Hordeum vulgare L.) Genotypes with contrasting drought tolerance behavior

“…This could explain the faster transition to the reproductive stage that occurred in Rum compared to Steptoe under LD and SD conditions and particularly in response to drought stress under SD conditions. Such differences in Vrn-H1 gene expression between genotypes were reported previously where higher expression levels were detected in S42-IL107 compared with Scarlett under LD conditions irrespective of drought treatment [21]. In this study, both tested genotypes carried different Vrn-H1 alleles where Rum has an insertion (Vrn-H1-7) and Steptoe has a deletion (Vrn-H1-4) at Vrn-H1 rst intron [22], which might explain the differential gene expression in response to different treatments.…”

“…A similar trend was reported by [51] where the developmental stage of the apical meristem was similar in introgression lines carrying Ppd-H1 under control and stress conditions. In a recent study, [21] found that the expression of Ppd-H1 was not affected in response to drought under LD conditions in two tested genotypes. Still, the same study concluded that Ppd-H1 integrates photoperiod and drought stress signals to ne-tune reproductive development in barley.…”

“…Allelic differences and their combinations in vernalization-(VRN) and photoperiodrelated (PPD) genes seem to have a large effect on stress tolerance in temperate cereals [18,19]. For instance, the PHOTOPERIOD-H1 (Ppd-H1) gene was found to control stress-induced senescence in barley roots subjected to osmotic stress [20] and most recently it was found to control the plasticity of development in response to drought [21]. In another study, barley genotypes carrying spring VERNALIZATION-H1 (Vrn-H1) alleles showed an accelerated owering under drought stress when compared with genotypes carrying winter alleles [22].…”

Novel exotic alleles of EARLY FLOWERING 3 determine plant development in barley

“…and HvBM8, barley homologues of Arabidopsis APETALA1/FRUITFUL (AP1/FUL), which were correlated with the development of inflorescence (Digel et al, 2015;Ejaz and von Korff, 2017;Gol et al, 2021). In contrast to Bowman, BW290, and HIF 10_190, we observed overall low VRN-H1 transcript abundance in HIF 10_003.…”

The circadian clock ticks in plant stress responses

“…Barley (Hordeum vulgare) photoperiod response gene PHOTOPERIOD-H1 (Ppd-H1) is a homolog to Arabidopsis PRR. Gol et al found that mild drought causes a decrease in the number of spikelet and a delay in floral development in spring barley cultivars with a natural mutation in ppd-H1, but has little effect on the introgression lines carrying wild-type Ppd-H1 (Gol et al, 2021). This result suggests the critical role of circadian component PRRs in potential drought adaptations.…”