Network Analysis of Different Exogenous Hormones on the Regulation of Deep Sowing Tolerance in Maize Seedlings

The Mechanism of Exogenous Salicylic Acid and 6-Benzylaminopurine Regulating the Elongation of Maize Mesocotyl

The elongation of the mesocotyl plays an important role in the emergence of maize deep-sowing seeds. This study was designed to explore the function of exogenous salicylic acid (SA) and 6-benzylaminopurine (6-BA) in the growth of the maize mesocotyl and to examine its regulatory network. The results showed that the addition of 0.25 mmol/L exogenous SA promoted the elongation of maize mesocotyls under both 3 cm and 15 cm deep-sowing conditions. Conversely, the addition of 10 mg/L exogenous 6-BA inhibited the elongation of maize mesocotyls. Interestingly, the combined treatment of exogenous SA-6-BA also inhibited the elongation of maize mesocotyls. The longitudinal elongation of mesocotyl cells was the main reason affecting the elongation of maize mesocotyls. Transcriptome analysis showed that exogenous SA and 6-BA may interact in the hormone signaling regulatory network of mesocotyl elongation. The differential expression of genes related to auxin (IAA), jasmonic acid (JA), brassinosteroid (BR), cytokinin (CTK) and SA signaling pathways may be related to the regulation of exogenous SA and 6-BA on the growth of mesocotyls. In addition, five candidate genes that may regulate the length of mesocotyls were screened by Weighted Gene Co-Expression Network Analysis (WGCNA). These genes may be involved in the growth of maize mesocotyls through auxin-activated signaling pathways, transmembrane transport, methylation and redox processes. The results enhance our understanding of the plant hormone regulation of mesocotyl growth, which will help to further explore and identify the key genes affecting mesocotyl growth in plant hormone signaling regulatory networks.

Dynamic physiological and transcriptomic changes reveal memory effects of salt stress in maize

BACKGROUND

Pre-exposing plants to abiotic stresses can induce stress memory, which is crucial for adapting to subsequent stress exposure. Although numerous genes involved in salt stress response have been identified, the understanding of memory responses to salt stress remains limited.

RESULTS

In this study, we conducted physiological and transcriptional assays on maize plants subjected to recurrent salt stress to characterize salt stress memory. During the second exposure to salt stress, the plants exhibited enhanced salt resistance, as evidenced by increased proline content and higher POD and SOD activity, along with decreased MDA content, indicative of physiological memory behavior. Transcriptional analysis revealed fewer differentially expressed genes and variations in response processes during the second exposure compared to the first, indicative of transcriptional memory behavior. A total of 2,213 salt stress memory genes (SMGs) were identified and categorized into four response patterns. The most prominent group of SMGs consisted of genes with elevated expression during the first exposure to salt stress but reduced expression after recurrent exposure to salt stress, or vice versa ([+ / -] or [- / +]), indicating that a revised response is a crucial process in plant stress memory. Furthermore, nine transcription factors (TFs) (WRKY40, WRKY46, WRKY53, WRKY18, WRKY33, WRKY70, MYB15, KNAT7, and WRKY54) were identified as crucial factors related to salt stress memory. These TFs regulate over 53% of SMGs, underscoring their potential significance in salt stress memory.

CONCLUSIONS

Our study demonstrates that maize can develop salt stress memory, and the genes identified here will aid in the genetic improvement of maize and other crops.

Exogenous strigolactones alleviate drought stress in wheat (Triticum aestivum L.) by promoting cell wall biogenesis to optimize root architecture

Exogenous strigolactones (SLs, GR24) are widely used to alleviate drought stress in wheat. The physiological and biochemical mechanisms via which SLs help overcome drought stress in wheat shoots have been reported; however, the mechanisms in wheat roots are unclear. The present study explored the effects of the exogenous application of SLs on wheat roots' growth and molecular responses under drought stress using physiological analysis and RNA-seq. RNA-seq of roots showed that SLs mainly upregulated signal transduction genes (SIS8, CBL3, GLR2.8, LRK10L-2.4, CRK29, and CRK8) and transcription factors genes (ABR1, BHLH61, and MYB93). Besides, SLs upregulated a few downstream target genes, including antioxidant genes (PER2, GSTF1, and GSTU6), cell wall biogenesis genes (SUS4, ADF3, UGT13248, UGT85A24, UGT709G2, BGLU31, and LAC5), an aquaporin-encoding gene (TIP4-3), and dehydrin-encoding genes (DHN2, DHN3, and DHN4). As a result, SLs reduced oxidative damage, optimized root architecture, improved leaf-water relation, and alleviated drought damage. Thus, the present study provides novel insights into GR24-mediated drought stress management and a scientific basis for proposing GR24 application.

Study on ZmRPN10 Regulating Leaf Angle in Maize by RNA-Seq

Ubiquitin/proteasome-mediated proteolysis (UPP) plays a crucial role in almost all aspects of plant growth and development, proteasome subunit RPN10 mediates ubiquitination substrate recognition in the UPP process. The recognition pathway of ubiquitinated UPP substrate is different in different species, which indicates that the mechanism and function of RPN10 are different in different species. However, the homologous ZmRPN10 in maize has not been studied. In this study, the changing of leaf angle and gene expression in leaves in maize wild-type B73 and mutant rpn10 under exogenous brassinosteroids (BRs) were investigated. The regulation effect of BR on the leaf angle of rpn10 was significantly stronger than that of B73. Transcriptome analysis showed that among the differentially expressed genes, CRE1, A-ARR and SnRK2 were significantly up-regulated, and PP2C, BRI1 AUX/IAA, JAZ and MYC2 were significantly down-regulated. This study revealed the regulation mechanism of ZmRPN10 on maize leaf angle and provided a promising gene resource for maize breeding.