Hua Xu

Soil salinization is a major abiotic stress limiting maize (Zea mays L.) growth and productivity worldwide. Recently, many genes involved in salt stress have been identified. However, the molecular mechanisms underlying salt tolerance in maize remain largely elusive. In this study, we identified a member of the ZmPIRIN family genes, ZmPRN1, acting as a negative regulator in response to salt stress. The expression levels of ZmPRN1 were down-regulated under salt and H₂O₂ treatment. Subcellular localization analysis showed that ZmPRN1 is localized to the chloroplast. Under salt stress, the Zmprn1-Mu mutant exhibited higher survival rates and lower reactive oxygen species (ROS) accumulation compared to wild-type plants. Whereas, ZmPRN1 overexpression lines were more sensitive to salt stress, and had higher ROS levels and lower chlorophyll content than wild-type plants. Transcriptome analysis showed that the differentially expressed genes (DEGs) were mainly involved in the oxidation-reduction process. Furthermore, yeast-two hybrid and split-luciferase complementation assays revealed that ZmPRN1 can interact with the chloroplast NDH complex subunit NDF4, the RING-type E3 ubiquitin ligase RING371, and the auxin-responsive protein IAA27. Collectively, our findings demonstrated that ZmPRN1 negatively regulates salt tolerance in maize by modulating ROS homeostasis, providing a valuable genetic resource for breeding salt-tolerant maize varieties.

Soil compaction poses a significant challenge in modern agriculture, as it constrains root development and hinders crop growth. The increasing evidence indicated that various phytohormones collaborate in distinct root zones to regulate root growth in compacted soils. However, the study of root development in maize under such conditions has been relatively limited. Here, we identified that the ZmSPL12 gene, belonging to the SPL transcription factor family, plays a crucial and positive role in regulating root development in the compacted soil. Specifically, the overexpression of ZmSPL12 resulted in significantly less inhibition of root growth than the wild-type plants when subjected to soil compaction. Histological analysis revealed that the capacity for root growth in compacted soil is closely associated with the development of the root cap. Further exploration demonstrated that ZmSPL12 modulates root growth through regulating ethylene signaling. Our findings underscored that ZmSPL12 expression level is induced by soil compaction and then enhances root penetration by regulating root cap and development, thereby enabling roots to thrive better in the compacted soil environment.

Maize (Zea mays) originated in southern Mexico and has spread over a wide latitudinal range. Maize expansion from tropical to temperate regions has necessitated a reduction of its photoperiod sensitivity. In this study, we cloned a quantitative trait locus (QTL) regulating flowering time in maize and show that the maize ortholog of Arabidopsis thaliana EARLY FLOWERING3, ZmELF3.1, is the causal locus. We demonstrate that ZmELF3.1 and ZmELF3.2 proteins can physically interact with ZmELF4.1/4.2 and ZmLUX1/2, to form evening complex(es; ECs) in the maize circadian clock. Loss-of-function mutants for ZmELF3.1/3.2 and ZmLUX1/2 exhibited delayed flowering under long-day and short-day conditions. We show that EC directly represses the expression of several flowering suppressor genes, such as the CONSTANS, CONSTANS-LIKE, TOC1 (CCT) genes ZmCCT9 and ZmCCT10, ZmCONSTANS-LIKE 3, and the PSEUDORESPONSE REGULATOR (PRR) genes ZmPRR37a and ZmPRR73, thus alleviating their inhibition, allowing florigen gene expression and promoting flowering. Further, we identify two closely linked retrotransposons located in the ZmELF3.1 promoter that regulate the expression levels of ZmELF3.1 and may have been positively selected during postdomestication spread of maize from tropical to temperate regions during the pre-Columbian era. These findings provide insights into circadian clock-mediated regulation of photoperiodic flowering in maize and new targets of genetic improvement for breeding.

Pectinases have many applications in the industry of food, paper, and textiles, therefore finding novel polygalacturonases is required. Multiple sequence alignment and phylogenetic analysis of AnEPG (an endo-α-1,4-polygalacturonase from Aspergillus nidulans) and other GH 28 endo-polygalacturonases suggested that AnEPG is different from others. AnEPG overexpressed in Pichia pastoris was characterized. AnEPG showed the highest activity at pH 4.0, and exhibited moderate activity over a narrow pH range (pH 2.0–5.0) and superior stability in a wide pH range (pH 2.0–12.0). It displayed the highest activity at 60 °C, and retained >42.2% of maximum activity between 20 and 80 °C. It was stable below 40 °C and lost activity very quickly above 50 °C. Its apparent kinetic parameters against PGA (polygalacturonic acid) were determined, with the K_m and k_cat values of 8.3 mg/mL and 5640 μmol/min/mg, respectively. Ba²⁺ and Ni²⁺ enhanced activity by 12.2% and 9.4%, respectively, while Ca²⁺, Cu²⁺, and Mn²⁺ inhibited activity by 14.8%, 12.8%, and 10.2% separately. Analysis of hydrolysis products by AnEPG proved that AnEPG belongs to an endo-polygalacturonase. Modelled structure of AnEPG by I-TASSER showed structural characteristics of endo-polygalacturonases. This pectinase has great potential to be used in food industry and as feed additives.

The bicolor Asiatic hybrid lily cultivar ‘Tiny Padhye’ is an attractive variety because of its unique color pattern. During its bicolor tepal development, the upper tepals undergo a rapid color change from green to white, while the tepal bases change from green to purple. However, the molecular mechanisms underlying these changes remain largely uncharacterized. To systematically investigate the dynamics of the lily bicolor tepal transcriptome during development, we generated 15 RNA-seq libraries from the upper tepals (S2-U) and basal tepals (S1-D, S2-D, S3-D, and S4-D) of Lilium ‘Tiny Padhye’. Utilizing the Illumina platform, a total of 295,787 unigenes were obtained from 713.12 million high-quality paired-end reads. A total of 16,182 unigenes were identified as differentially expressed genes during tepal development. Using Kyoto Encyclopedia of Genes and Genomes pathway analysis, candidate genes involved in the anthocyanin biosynthetic pathway (61 unigenes) and chlorophyll metabolic pathway (106 unigenes) were identified. Further analyses showed that most anthocyanin biosynthesis genes were transcribed coordinately in the tepal bases, but not in the upper tepals, suggesting that the bicolor trait of ‘Tiny Padhye’ tepals is caused by the transcriptional regulation of anthocyanin biosynthetic genes. Meanwhile, the high expression level of chlorophyll degradation genes and low expression level of chlorophyll biosynthetic genes resulted in the absence of chlorophylls from ‘Tiny Padhye’ tepals after flowering. Transcription factors putatively involved in the anthocyanin biosynthetic pathway and chlorophyll metabolism in lilies were identified using a weighted gene co-expression network analysis and their possible roles in lily bicolor tepal development were discussed. In conclusion, these extensive transcriptome data provide a platform for elucidating the molecular mechanisms of bicolor tepals in lilies and provide a basis for similar research in other closely related species.