To better understand abscisic acid (ABA) regulation of the synthesis of chloroplast proteins in maize (Zea mays L.) in response to drought and light, we compared leaf proteome differences between maize ABA-deficient mutant vp5 and corresponding wild-type Vp5 green and etiolated seedlings exposed to drought stress. Proteins extracted from the leaves of Vp5 and vp5 seedlings were used for two-dimensional electrophoresis (2-DE) and subsequent matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS). After Coomassie brilliant blue staining, approximately 450 protein spots were reproducibly detected on 2-DE gels. A total of 36 differentially expressed protein spots in response to drought and light were identified using MALDI-TOF MS and their subcellular localization was determined based on the annotation of reviewed accession in UniProt Knowledgebase and the software prediction. As a result, corresponding 13 proteins of the 24 differentially expressed protein spots were definitely localized in chloroplasts and their expression was in an ABA-dependent way, including 6 up-regulated by both drought and light, 5 up-regulated by drought but down-regulated by light, 5 up-regulated by light but down-regulated by drought; 5 proteins down-regulated by drought were mainly those involved in photosynthesis and ATP synthesis. Thus, the results in the present study supported the vital role of ABA in regulating the synthesis of drought- and/or light-induced proteins in maize chloroplasts and would facilitate the functional characterization of ABA-induced chloroplast proteins in C₄ plants.

Abscisic acid (ABA) regulates various developmental processes and stress responses in plants. Protein phosphorylation/dephosphorylation is a central post-translational modification (PTM) in ABA signaling. However, the phosphoproteins regulated by ABA under osmotic stress remain unknown in maize. In this study, maize mutant vp5 (deficient in ABA biosynthesis) and wild-type Vp5 were used to identify leaf phosphoproteins regulated by ABA under osmotic stress. Up to 4052 phosphopeptides, corresponding to 3017 phosphoproteins, were identified by Multiplex run iTRAQ-based quantitative proteomic and LC-MS/MS methods. The 4052 phosphopeptides contained 5723 non-redundant phosphosites; 512 phosphopeptides (379 in Vp5, 133 in vp5) displayed at least a 1.5-fold change of phosphorylation level under osmotic stress, of which 40 shared common in both genotypes and were differentially regulated by ABA. Comparing the signaling pathways involved in vp5 response to osmotic stress and those that in Vp5, indicated that ABA played a vital role in regulating these pathways related to mRNA synthesis, protein synthesis and photosynthesis. Our results provide a comprehensive dataset of phosphopeptides and phosphorylation sites regulated by ABA in maize adaptation to osmotic stress. This will be helpful to elucidate the ABA-mediate mechanism of maize endurance to drought by triggering phosphorylation or dephosphorylation cascades.

Studying the canopy spectral reflection characteristics of different N-efficient maize varieties and analyzing the relationship between their growth indicators and spectral vegetation indices can help the breeding and application of N-efficient maize varieties. To achieve the optimal management of N fertilizer resources, developing N-efficient maize varieties is necessary. In this research, maize varieties, i.e., the low-N-efficient (Zhengdan 958, ZD958), the high-N efficient (Xianyu 335, XY335), the double-high varieties (Qiule 368, QL368), and the double inefficient-type varieties (Yudan 606 YD606), were used as materials. Results indicate that nitrogen fertilization significantly increased the vegetation indices NDVI, GNDVI, GOSAVI, and RVI of maize varieties with different nitrogen efficiencies. These findings were consistent with the performance of yield, dry matter mass, and leaf nitrogen content and were also found highest under both medium and high nitrogen conditions in the double-high variety QL368. The correlations of dry matter quality, leaf nitrogen content, yield, and vegetation indices (NDVI, GNDVI, RVI, and GOSAVI) at the filling stage of different N-efficient maize varieties were all highly significant and positive. In this relationship, the best effect was found at the filling stages, with correlation coefficients reaching 0.772–0.942, 0.774–0.970, 0754–0.960, and 0.800–0.960. The results showed that the yield, dry matter weight, and leaf nitrogen content of maize varieties with different nitrogen efficiencies increased first and then stabilized with the increase in the nitrogen application level in different periods, and the highest nitrogen application level of maize yield should be between 270 and 360 kg/hm². At the filling stage, canopy vegetation index of maize varieties with different nitrogen efficiencies was positively correlated with yield, dry matter weight, and leaf nitrogen content, especially GNDVI and GOSAVI on the leaf nitrogen content. It can be used as a means to predict its growth index.

Introduction: Crop diversification is a critical strategy for improving resource use efficiency and suppressing disease. Mixing cultivars from the same crop is one approach to diversifying planting patterns. However, it remains unknown how mixing cultivars in maize affects the soil microbial community, stalk rot incidence, and grain yield. Methods: A 2-year field experiment was performed, which included one stalk rot-resistance cultivar, DH662; one stalk rot-susceptible cultivar, DH701; and a mixture of DH662 and DH701. Results: Cultivar mixtures and DH662 monocrop had lower disease incidence and higher grain yield than DH701 monocrop. The microbial community structure in both rhizosphere and bulk soil was notably impacted by the resistant cultivar as well as the cultivar mixtures. Distinct modules within the rhizosphere microbial community co-occurrence network were identified, differentiating cultivar mixtures from DH701 monocrops. The network structure of the rhizosphere in cultivar mixtures closely resembled that observed in DH662 monocrops. Keystone taxa were higher in cultivar mixtures compared to their abundance in DH701 monocrops. The keystone taxa ( Adhaeribacter and Gemmatimonas ) were positively related to grain yield and negatively correlated with disease incidence. Discussion: Overall, our results demonstrated that cultivar mixtures had a substantial impact on the assembly and keystone taxa of microbial communities in the rhizosphere and bulk soil, leading to a reduction in stalk rot occurrence and an increase in grain yield. This study demonstrated the potential for maize yield improvement through cultivar mixtures. These findings improved insights into how beneficial microbial communities in the rhizosphere contributed to the positive effects observed in cultivar mixtures.