Forkhead transcription factor Fkh1: insights into functional regulatory domains crucial for recruitment of Sin3 histone deacetylase complex.

Transcription factors are inextricably linked with histone deacetylases leading to compact chromatin. The Forkhead transcription factor Fkh1 is mainly a negative transcriptional regulator which affects cell cycle control, silencing of mating-type cassettes and induction of pseudohyphal growth in the yeast Saccharomyces cerevisiae. Markedly, Fkh1 impinges chromatin architecture by recruiting large regulatory complexes. Implication of Fkh1 with transcriptional corepressor complexes remains largely unexplored. In this work we show that Fkh1 directly recruits corepressors Sin3 and Tup1 (but not Cyc8), providing evidence for its influence on epigenetic regulation. We also identified the specific domain of Fkh1 mediating Sin3 recruitment and substantiated that amino acids 51-125 of Fkh1 bind PAH2 of Sin3. Importantly, this part of Fkh1 overlaps with its Forkhead-associated domain (FHA). To analyse this domain in more detail, selected amino acids were replaced by alanine, revealing that hydrophobic amino acids L74 and I78 are important for Fkh1-Sin3 binding. In addition, we could prove Fkh1 recruitment to promoters of cell cycle genes CLB2 and SWI5. Notably, Sin3 is also recruited to these promoters but only in the presence of functional Fkh1. Our results disclose that recruitment of Sin3 to Fkh1 requires precisely positioned Fkh1/Sin3 binding sites which provide an extended view on the genetic control of cell cycle genes CLB2 and SWI5 and the mechanism of transcriptional repression by modulation of chromatin architecture at the G2/M transition.

Impact of heat and drought stress on peroxisome proliferation in quinoa.

Although peroxisomes play a key role in plant metabolism under both normal and stressful growth conditions, the impact of drought and heat stress on the peroxisomes remains unknown. Quinoa represents an informative system for dissecting the impact of abiotic stress on peroxisome proliferation because it is adapted to marginal environments. Here we determined the correlation of peroxisome abundance with physiological responses and yield under heat, drought and heat plus drought stresses in eight genotypes of quinoa. We found that all stresses caused a reduction in stomatal conductance and yield. Furthermore, H2 O2 content increased under drought and heat plus drought. Principal component analysis demonstrated that peroxisome abundance correlated positively with H2 O2 content in leaves and correlated negatively with yield. Pearson correlation coefficient for yield and peroxisome abundance (r = -0.59) was higher than for commonly used photosynthetic efficiency (r = 0.23), but comparable to those for classical stress indicators such as soil moisture content (r = 0.51) or stomatal conductance (r = 0.62). Our work established peroxisome abundance as a cellular sensor for measuring responses to heat and drought stress in the genetically diverse populations. As heat waves threaten agricultural productivity in arid climates, our findings will facilitate identification of genetic markers for improving yield of crops under extreme weather patterns.

Effect of long-term heat stress on grain yield, pollen grain viability and germinability in bread wheat (Triticum aestivum L.) under field conditions.

Frequent episodes of heat threaten sustainable agriculture in Egypt. This study is an urgent call to select tolerant genotypes of heat and discover the predicted screening phenotypic parameters. Here, twenty spring wheat genotypes were exposed to heat stress under field conditions for screening heat tolerance. Stress environments were simulated by delaying the sowing date by 53 and 58 days than the normal environments for two successive seasons. Stressed plants received the highest peak of heat during the reproductive growth stage. Eight phenotypic parameters were measured to evaluate genotype tolerance. Mean performance, reduction percentage/trait, and heat susceptibility index parameters were calculated. Additionally, the pollen grain viability during spike emergence and the germinability of producing grains were investigated. Results demonstrated: (1) Highly significant differences (P < 0.01) between genotypes, treatments and genotypes by treatments in grain yield and other traits in both studied seasons, (2) significant reduction in all studied traits compared to the non-stress environment, (3) the overall yield reduction, based on grain yield/m2, was 40.17, 41.19 % in the first and second seasons, respectively, and the most tolerant genotypes were Masr2, Sids1, Giza 171 and Line 9, (4) limited impact of heat has detected on pollen grains viability and germinability, and (5) grain yield as a selection criterion for heat stress remains the most reliable yardstick.

Corrigendum to "Effects of Climate Temperature and Water Stress on Plant Growth and Accumulation of Antioxidant Compounds in Sweet Basil (Ocimum basilicum L.) Leafy Vegetable".

[This corrects the article DOI: 10.1155/2020/3808909.].

Differential Dynamic Changes of Reduced Trait Model for Analyzing the Plastic Response to Drought Phases: A Case Study in Spring Wheat.

Current limited water availability due to climate changes results in severe drought stress and desiccation in plants. Phenotyping drought tolerance remains challenging. In particular, our knowledge about the discriminating power of traits for capturing a plastic phenotype in high-throughput settings is scant. The study is designed to investigate the differential performance and broad-sense heritability of a battery set of morphological, physiological, and cellular traits to understand the adaptive phenotypic response to drought in spring wheat during the tillering stage. The potential of peroxisome abundance to predict the adaptive response under severe drought was assessed using a high-throughput technique for peroxisome quantification in plants. The research dissected the dynamic changes of some phenological traits during three successive phases of drought using two contrasting genotypes of adaptability to drought. The research demonstrates 5 main findings: (1) a reduction of the overall dimension of the phenological traits for robust phenotyping of the adaptive performance under drought; (2) the abundance of peroxisomes in response to drought correlate negatively with grain yield; (3) the efficiency of ROS homeostasis through peroxisome proliferation which seems to be genetically programmed; and (4) the dynamics of ROS homeostasis seems to be timing dependent mechanism, the tolerant genotype response is earlier than the susceptible genotype. This work will contribute to the identification of robust plastic phenotypic tools and the understanding of the mechanisms for adaptive behavior under drought conditions. SUMMARY STATEMENT: This study presents the estimated broad-sense heritability of 24 phenological traits under drought compared with non-stressed conditions. The results demonstrated a reduced model of the overall dimension of the phenological traits for phenotyping drought tolerant response including a novel trait (peroxisome abundance). Also, it displays that the adaptive mechanism through peroxisomes proliferation that is a genetic-dependent manner and related to the stress phase, since tolerant plants can sense the stress and maintain the cellular balance earlier than the sensitive plants.

Impact of salt stress, cell death, and autophagy on peroxisomes: quantitative and morphological analyses using small fluorescent probe N-BODIPY.

Plant peroxisomes maintain a plethora of key life processes including fatty acid ß-oxidation, photorespiration, synthesis of hormones, and homeostasis of reactive oxygen species (ROS). Abundance of peroxisomes in cells is dynamic; however mechanisms controlling peroxisome proliferation remain poorly understood because measuring peroxisome abundance is technically challenging. Counting peroxisomes in individual cells of complex organs by electron or fluorescence microscopy is expensive and time consuming. Here we present a simple technique for quantifying peroxisome abundance using the small probe Nitro-BODIPY, which in vivo fluoresces selectively inside peroxisomes. The physiological relevance of our technique was demonstrated using salinity as a known inducer of peroxisome proliferation. While significant peroxisome proliferation was observed in wild-type Arabidopsis leaves following 5-hour exposure to NaCl, no proliferation was detected in the salt-susceptible mutants fry1-6, sos1-14, and sos1-15. We also found that N-BODIPY detects aggregation of peroxisomes during final stages of programmed cell death and can be used as a marker of this stage. Furthermore, accumulation of peroxisomes in an autophagy-deficient Arabidopsis mutant atg5 correlated with N-BODIPY labeling. In conclusion, the technique reported here enables quantification of peroxisomes in plant material at various physiological settings. Its potential applications encompass identification of genes controlling peroxisome homeostasis and capturing stress-tolerant genotypes.

Developmental program impacts phenological plasticity of spring wheat under drought.

BACKGROUND: Developing drought-tolerant crops critically depends on the efficient response of a genotype to the limited water availability, a trait known as phenological plasticity. Our understanding of the phenological plasticity remains limited, in particular, about its relationships with plant developmental program. Here, we examined the plastic response of spring wheat at tillering, booting, heading, and anthesis stages to constant or periodic drought stress. The response was assessed by morphological and physiological parameters including symptoms. RESULTS: The dynamics of morphological symptoms were indicators of the plasticity identification of drought. We found that spring wheat exhibits higher phenological plasticity during tillering stage followed by the heading stage, while booting and anthesis stages are the most sensitive. Also, the adaptive response is thought to be influenced with the plant height genes. Furthermore, periodic stress caused more pronounced inhibition of yield than the constant stress, with limited resistance resolution under long period. CONCLUSIONS: Our study shows the importance of considering the phenological plasticity in designing screens for drought tolerance in spring wheat and proposes tillering as the most informative stage for capturing genotypes with tolerance to limit water availability.