Functional characterization of MaEXPA11 and its roles in response to biotic and abiotic stresses in mulberry

Genome-Wide Analysis of NAC Transcription Factor Gene Family in Morus atropurpurea

The NAC (NAM/ATAF1/2/CUC2) transcription factors are pivotal regulators in plant development and stress responses. Despite the extensive studies on the NAC gene family across various plant species, the characterization of this gene family in mulberry (Morus atropurpurea) remains unexplored. Here, we conducted a genome-wide identification and characterization of the NAC gene family in M. atropurpurea. A total of 79 MaNAC genes were identified and classified into 20 subgroups, displaying an uneven distribution across the 14 chromosomes. The structural analysis found that most MaNAC genes possess at least three exons and contain the conserved NAC domain and characteristic motifs at the N-terminus. Eleven collinear gene pairs were identified in M. atropurpurea genome. Interspecies collinearity analysis demonstrated a closer evolutionary relationship between M. atropurpurea and Populus trichocarpa, supported by the identification of 116 collinear gene pairs. Expression profiling revealed dynamic changes in the transcript levels of most MaNAC genes during mulberry fruit maturation. Notably, the eight MaNAC members from the OsNAC7 subfamily exhibited tissue-specific expression patterns. A significant proportion of MaNAC genes displayed varying degrees of responsiveness to drought stress and sclerotium disease. MaNAC12, MaNAC32, MaNAC44 and MaNAC67 emerged as the most highly responsive candidates. Overexpression of MaNAC69 enhanced drought tolerance in Arabidopsis. These findings provide a robust foundation for future functional studies and mechanistic investigations into the roles of the NAC gene family in M. atropurpurea, offering insights into their contributions to development and stress adaptation.

The transcriptional response to yellow and wilt disease, caused by race 6 of Fusarium oxysporum f. sp. Ciceris in two contrasting chickpea cultivars

BACKGROUND

Chickpea (Cicer arietinum L.) ranks as the third most crucial grain legume worldwide. Fusarium wilt (Fusarium oxysporum f. sp. ciceri (Foc)) is a devastating fungal disease that prevents the maximum potential for chickpea production.

RESULTS

To identify genes and pathways involved in resistance to race 6 of Foc, this study utilized transcriptome sequencing of two chickpea cultivars: resistant (Ana) and susceptible (Hashem) to Foc race 6. Illumina sequencing of the root samples yielded 133.5 million raw reads, with about 90% of the clean reads mapped to the chickpea reference genome. The analysis revealed that 548 genes (332 upregulated and 216 downregulated) in the resistant genotype (Ana) and 1115 genes (595 upregulated and 520 downregulated) in the susceptible genotype (Hashem) were differentially expressed under Fusarium wilt (FW) disease stress caused by Foc race 6. The expression patterns of some differentially expressed genes (DEGs) were validated using quantitative real-time PCR. A total of 131 genes were exclusively upregulated under FW stress in the resistant cultivar, including several genes involved in sensing (e.g., CaNLR-RPM1, CaLYK5-RLK, CaPR5-RLK, CaLRR-RLK, and CaRLP-EIX2), signaling (e.g., CaPP7, CaEPS1, CaSTY13, and CaPR-1), transcription regulation (e.g., CaMYBs, CaGLK, CaERFs, CaZAT11-like, and CaNAC6) and cell wall integrity (e.g., CaPGI2-like, CaEXLs, CaCSLD and CaCYP73A100-like).

CONCLUSIONS

The achieved results could provide insights into the molecular mechanism underlying resistance to FW and could be valuable for breeding programs aimed at developing FW-resistant chickpea varieties.

The SmWRKY12-SmRAP2-7-SmEXPA13 module in Salix matsudana koidz enhances plant tolerance to drought stress

WRKY transcription factors play key roles in plant responses to abiotic stress. In this study, we cloned and characterized the drought-induced WRKY gene SmWRKY12 from Salix matsudana Koidz. Following drought treatment, SmWRKY12 was significantly upregulated in the roots of the drought-tolerant willow variety 9901. Overexpressing SmWRKY12 in willow calli significantly increased drought tolerance. The results of yeast one-hybrid and dual-luciferase reporter assays showed that SmWRKY12 can bind to the promoter of the expansin gene SmEXPA13 and activate its expression. The results of yeast two-hybrid and split luciferase complementation assays showed that SmWRKY12 can interact with SmRAP2-7. The results of dual-luciferase and transgenic experiments showed that the combination of SmWRKY12 and SmRAP2-7 significantly increased the transcriptional regulation of SmWRKY12 on SmEXPA13. SmEXPA13 was introduced into willow calli and tobacco plants. Overexpressing SmEXPA13 significantly improved their performance under drought conditions. The results revealed a novel mechanism to tolerate drought stress through the SmWRKY12-SmRAP2-7-SmEXPA13 module in willow. This study also provided a new strategy for the molecular design and breeding of drought-tolerant plants.

Identification and characterization of a rice expansin-like protein with metal-binding properties

Heavy metal (HM) contamination poses significant threat to agricultural productivity. This study identified and characterized Os09g29690 (OsELP), a rice expansin-like protein. We demonstrated OsELP localizes to the cell wall and is upregulated under various abiotic stresses. Sequence analysis revealed a potential metal-binding CXXXC motif in its conserved domain. Heterologous expression of OsELP in yeast mutants (Δacr3 and Δycf1) enhanced metal tolerance under arsenate [As(V)], arsenite [As(III)], and cadmium [Cd] stress. Yeast cells expressing OsELP accumulated higher amounts of As and Cd, suggesting a potential metal-binding mechanism. This was confirmed through site-directed mutagenesis on the conserved cysteine and serine residues within OsELP. Mutants lacking cysteine residues (mutCS) reduced tolerance to As(III) and Cd but enhanced tolerance to As(V), indicating a role of cysteine in As(III) and Cd binding. Conversely, mutants lacking serine residues (mutSA) reduced tolerance to As(V), suggesting serine's involvement in As(V) binding. These findings reveal the roles of cysteine and serine residues in mediating HM tolerance and binding, confirming OsELP as a key player in HM detoxification through cell wall localization and chelation. This study provides novel insights into the molecular mechanisms of HM tolerance in plants, with potential applications in developing crops with enhanced resistance to HM toxicity.

The Functional Characterization of MaGS2 and Its Role as a Negative Regulator of Ciboria shiraiana

Glutamine synthetase (GS) is a key enzyme involved in nitrogen metabolism. GS can be divided into cytosolic and plastidic subtypes and has been reported to respond to various biotic and abiotic stresses. However, little research has been reported on the function of GS in mulberry. In this study, the full length of MaGS2 was cloned, resulting in 1302 bp encoding 433 amino acid residues. MaGS2 carried the typical GS2 motifs and clustered with plastidic-subtype GSs in the phylogenetic analysis. MaGS2 localized in chloroplasts, demonstrating that MaGS2 is a plastidic GS. The expression profile showed that MaGS2 is highly expressed in sclerotiniose pathogen-infected fruit and sclerotiniose-resistant fruit, demonstrating that MaGS2 is associated with the response to sclerotiniose in mulberry. Furthermore, the overexpression of MaGS2 in tobacco decreased the resistance against Ciboria shiraiana, and the knockdown of MaGS2 in mulberry by VIGS increased the resistance against C. shiraiana, demonstrating the role of MaGS2 as a negative regulator of mulberry resistance to C. shiraiana infection.

PagEXPA1 combines with PagCDKB2;1 to regulate plant growth and the elongation of fibers in Populus alba × Populus glandulosa

Expansins are important plant cell wall proteins. They can loosen and soften the cell walls and lead to wall extension and cell expansion. To investigate their role in wood formation and fiber elongation, the PagEXPA1 that highly expressed in cell differentiation and expansion tissues was cloned from 84K poplar (Populus alba × P. glandulosa). The subcellular localization showed that PagEXPA1 located in the cell wall and it was highly expressed in primary stems and young leaves. Compared with non-transgenic 84K poplar, overexpression of PagEXPA1 can promote plant-growth, lignification, and fiber cell elongation, while PagEXPA1 Cas9-editing mutant lines exhibited the opposite phenotype. Transcriptome analysis revealed that DEGs were mainly enriched in some important processes, which are associated with cell wall formation and cellulose synthesis. The protein interaction prediction and expression analysis showed that PagCDKB2:1 and PagEXPA1 might have an interaction relationship. The luciferase complementary assay and bimolecular fluorescence complementary assay validated that PagEXPA1 can combined with PagCDKB2;1. So they promoted the expansion of xylem vascular tissues and the development of poplar though participating in the regulation of cell division and differentiation by programming the cell-cycle. It provides good foundation for molecular breeding of fast-growing and high-quality poplar varieties.