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Summary: Transcriptional regulation mechanisms underlying chilling injury (CI) development have been widely investigated in model plants and cold‐sensitive fruits, such as banana (Musa acuminata). However, unlike the well‐known NAC and WRKY transcription factors (TFs), the function and deciphering mechanism of heat shock factors (HSFs) involving in cold response are still fragmented. Here, we showed that hot water treatment (HWT) alleviated CI in harvested banana fruits accomplishing with reduced reactive oxygen species (ROS) accumulation and increased antioxidant enzyme activities. A cold‐inducible but HWT‐inhibited HSF, MaHsf24, was identified. Using DNA affinity purification sequencing (DAP‐seq) combined with RNA‐seq analyses, we found three heat shock protein (HSP) genes (MaHSP23.6, MaHSP70‐1.1 and MaHSP70‐1.2) and three antioxidant enzyme genes (MaAPX1, MaMDAR4 and MaGSTZ1) were the potential targets of MaHsf24. Subsequent electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation coupled with quantitative PCR (ChIP‐qPCR) and dual‐luciferase reporter (DLR) analyses demonstrated that MaHsf24 repressed the transcription of these six targets via directly binding to their promoters. Moreover, stably overexpressing MaHsf24 in tomatoes increased cold sensitivity by suppressing the expressions of HSPs and antioxidant enzyme genes, while HWT could recover cold tolerance, maintaining higher levels of HSPs and antioxidant enzyme genes, and activities of antioxidant enzymes. In contrast, transiently silencing MaHsf24 by virus‐induced gene silencing (VIGS) in banana peels conferred cold resistance with the upregulation of MaHSPs and antioxidant enzyme genes. Collectively, our findings support the negative role of MaHsf24 in cold tolerance, and unravel a novel regulatory network controlling bananas CI occurrence, concerning MaHsf24‐exerted inhibition of MaHSPs and antioxidant enzyme genes. [ABSTRACT FROM AUTHOR]

High temperatures (>24°C) prevent the development of a yellow peel on bananas called green ripening, owing to the inhibition of chlorophyll degradation. This phenomenon greatly reduces the marketability of banana fruit, but the mechanisms underlining high temperature‐repressed chlorophyll catabolism need to be elucidated. Herein, we found that the protein accumulation of chlorophyll catabolic enzyme MaSGR1 (STAY‐GREEN 1) was reduced when bananas ripened at high temperature. Transiently expressing MaSGR1 in banana peel showed its positive involvement in promoting chlorophyll degradation under high temperature, thereby weakening green ripening phenotype. Using yeast two‐hybrid screening, we identified a RING‐type E3 ubiquitin ligase, MaRZF1 (RING Zinc Finger 1), as a putative MaSGR1‐interacting protein. MaRZF1 interacts with and targets MaSGR1 for ubiquitination and degradation via the proteasome pathway. Moreover, upregulating MaRZF1 inhibited chlorophyll degradation, and attenuated MaSGR1‐promoted chlorophyll degradation in bananas during green ripening, indicating that MaRZF1 negatively regulates chlorophyll catabolism via the degradation of MaSGR1. Taken together, MaRZF1 and MaSGR1 form a regulatory module to mediate chlorophyll degradation associated with high temperature‐induced green ripening in bananas. Therefore, our findings expand the understanding of posttranslational regulatory mechanisms of temperature stress‐caused fruit quality deterioration. Summary statement: RING‐type ubiquitin E3 ligase MaRZF1 interacts with chlorophyll catabolic enzyme MaSGR1, which promotes the ubiquitination and proteasomal degradation of MaSGR1, causing the green ripening of banana fruit under high temperature. [ABSTRACT FROM AUTHOR]

Summary: Chilling injury has a negative impact on the quantity and quality of crops, especially subtropical and tropical plants. The plant cell wall is not only the main source of biomass production, but also the first barrier to various stresses. Therefore, improving the understanding of the alterations in cell wall architecture is of great significance for both biomass production and stress adaptation. Herein, we demonstrated that the cell wall principal component cellulose accumulated during chilling stress, which was caused by the activation of MaCESA proteins. The sequence‐multiple comparisons show that a cold‐inducible NAC transcriptional factor MaNAC1, a homologue of Secondary Wall NAC transcription factors, has high sequence similarity with Arabidopsis SND3. An increase in cell wall thickness and cellulosic glucan content was observed in MaNAC1‐overexpressing Arabidopsis lines, indicating that MaNAC1 participates in cellulose biosynthesis. Over‐expression of MaNAC1 in Arabidopsis mutant snd3 restored the defective secondary growth of thinner cell walls and increased cellulosic glucan content. Furthermore, the activation of MaCESA7 and MaCESA6B cellulose biosynthesis genes can be directly induced by MaNAC1 through binding to SNBE motifs within their promoters, leading to enhanced cellulose content during low‐temperature stress. Ultimately, tomato fruit showed greater cold resistance in MaNAC1 overexpression lines with thickened cell walls and increased cellulosic glucan content. Our findings revealed that MaNAC1 performs a vital role as a positive modulator in modulating cell wall cellulose metabolism within banana fruit under chilling stress. [ABSTRACT FROM AUTHOR]

Gently inclined weak interlayer is one of important factors affecting anti-sliding stability of dam foundation. The densely developed gently inclined weak interlayer makes the stability of dam foundation more complicated. It is of great significance to engineering safety and treatment of dam foundation under complex foundation conditions to study the instability mode of dam foundation under the influence of dense gently inclined weak interlayer. In this paper, two typical dam sections of Datengxia Sluice Dam are studied by using geomechanical model and numerical simulation method respectively. In this study, the adverse effects of dense gently inclined weak interlayer and faults are taken into full consideration, and the failure process and form of the dam foundation are obtained. The stability safety factor of the comprehensive method is determined to be KSC=3.30-4.18. It is revealed that the failure mode of the dam foundation of Datengxia Sluice Gate is the compression yield failure of shallow bedrock, and the gently inclined weak interlayer does not form a slip channel. No deep sliding failure occurs in the dam foundation. The results show that the dam heel area and the dam toe area are the weak parts of the project, which needs to be strengthened by engineering measures. The research results provide an important basis for the design of engineering reinforcement scheme and a reference for similar engineering dam foundation stability researches. [ABSTRACT FROM AUTHOR]