Functional characterization of maize phytochrome-interacting factor 3 (ZmPIF3) in enhancing salt tolerance in arabidopsis.

Soil salinization, a prevalent form of environmental stress, leads to significant soil desertification and impacts agricultural productivity by altering the internal soil environment, slowing cellular metabolism, and modifying cellular architecture. This results in a marked reduction in both the yield and diversity of crops. Maize, which is particularly susceptible to salt stress, serves as a critical model for studying these effects, making the elucidation of its molecular responses essential for crop improvement strategies. This study focuses on the phytochrome-interacting factor 3 (PIF3), previously known for its role in freezing tolerance, to assess its function in salt stress tolerance. Utilizing two transcript variants of maize ZmPIF3 (ZmPIF3.1 and ZmPIF3.2), we engineered Arabidopsis transgenic lines to overexpress these variants and analyzed their phenotypic, physiological, biochemical, and transcriptomic responses to salt stress. Our findings reveal that these transgenic lines displayed not only enhanced salt tolerance but also improved peroxide decomposition and reduced cellular membrane damage. Transcriptome analysis indicated significant roles of hormonal and Ca2+ signaling pathways, along with key transcription factors, in mediating the enhanced salt stress response. This research underscores a novel role for ZmPIF3 in plant salt stress tolerance, offering potential avenues for breeding salt-resistant crop varieties.

ZmCCA1a on Chromosome 10 of Maize Delays Flowering of Arabidopsis thaliana.

Maize (Zea mays) is a major cereal crop that originated at low latitudes, and thus photoperiod sensitivity is an important barrier to the use of tropical/subtropical germplasm in temperate regions. However, studies of the mechanisms underlying circadian regulation in maize are at an early stage. In this study we cloned ZmCCA1a on chromosome 10 of maize by map-based cloning. The gene is homologous to the Myb transcription factor genes AtCCA1/AtLHY in Arabidopsis thaliana; the deduced Myb domain of ZmCCA1a showed high similarity with that of AtCCA1/AtLHY and ZmCCA1b. Transiently or constitutively expressed ZmCCA1a-YFPs were localized to nuclei of Arabidopsis mesophyll protoplasts, agroinfiltrated tobacco leaves, and leaf and root cells of transgenic seedlings of Arabidopsis thaliana. Unlike AtCCA1/AtLHY, ZmCCA1a did not form homodimers nor interact with ZmCCA1b. Transcripts of ZmCCA1a showed circadian rhythm with peak expression around sunrise in maize inbred lines CML288 (photoperiod sensitive) and Huangzao 4 (HZ4; photoperiod insensitive). Under short days, transcription of ZmCCA1a in CML288 and HZ4 was repressed compared with that under long days, whereas the effect of photoperiod on ZmCCA1a expression was moderate in HZ4. In ZmCCA1a-overexpressing A. thaliana (ZmCCA1a-ox) lines, the circadian rhythm was disrupted under constant light and flowering was delayed under long days, but the hypocotyl length was not affected. In addition, expression of endogenous AtCCA1/AtLHY and the downstream genes AtGI, AtCO, and AtFt was repressed in ZmCCA1a-ox seedlings. The present results suggest that the function of ZmCCA1a is similar, at least in part, to that of AtCCA1/AtLHY and ZmCCA1b, implying that ZmCCA1a is likely to be an important component of the circadian clock pathway in maize.

Alternative splicing of ZmCCA1 mediates drought response in tropical maize.

The circadian clock regulates numerous biological processes in plants, especially development and stress responses. CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1) is one of the core components of the day-night rhythm response and is reportedly associated with ambient temperature in Arabidopsis thaliana. However, it remains unknown if alternative splicing of ZmCCA1 is modulated by external stress in maize, such as drought stress and photoperiod. Here, we identified three ZmCCA1 splice variants in the tropical maize line CML288, which are predicted to encode three different protein isoforms, i.e., ZmCCA1.1, ZmCCA1.2, and ZmCCA1.3, which all retain the MYB domain. In maize, the expression levels of ZmCCA1 splice variants were influenced by photoperiod, tissue type, and drought stress. In transgenic A. thaliana, ZmCCA1.1 may be more effective than ZmCCA1.3 in increasing drought tolerance while ZmCCA1.2 may have only a small effect on tolerance to drought stress. Additionally, although CCA1 genes have been found in many plant species, alternative CCA1 splicing events are known to occur in species-specific ways. Our study provides new sight to explore the function of ZmCCA1 splice variants' response to abiotic stress, and clarify the linkage between circadian clock and environmental stress in maize.