Chestnut (Castanea mollissima Blume) is an important economic tree owing to its tasty fruit and adaptability to environmental stresses, especially drought. Currently, there is limited information about non-specific lipid transfer protein (nsLTP) genes that respond to abiotic stress in chestnuts. Here, a chestnut nsLTP, named CmnsLTP6.9, was identified and analyzed. The results showed that the CmnsLTP6.9 protein localized in the extracellular matrix had two splicing variants (CmnsLTP6.9L and CmnsLTP6.9S). Compared with CmnsLTP6.9L, CmnsLTP6.9S had an 87 bp deletion in the 5′-terminal. Overexpression of CmnsLTP6.9L in Arabidopsis enhanced tolerance to osmotic and drought stress. Upon exposure to osmotic and drought treatment, CmnsLTP6.9L could increase reactive oxygen species (ROS)-scavenging enzyme activity, alleviating ROS damage. However, CmnsLTP6.9S-overexpressing lines showed no significant differences in phenotype, ROS content, and related enzyme activities compared with the wild type (WT) under osmotic and drought treatment. Moreover, lipid metabolism analysis confirmed that, unlike CmnsLTP6.9S, CmnsLTP6.9L mainly altered and upregulated many fatty acyls and glycerophospholipids, which implied that CmnsLTP6.9L and CmnsLTP6.9S played different roles in lipid transference in the chestnut. Taken together, we analyzed the functions of CmnsLTP6.9L and CmnsLTP6.9S, and demonstrated that CmnsLTP6.9L enhanced drought and osmotic stress tolerance through ROS scavenging and lipid metabolism.

Dwarfing is an important agronomic characteristic in fruit breeding. However, due to the lack of dwarf cultivars and dwarf stocks, the dwarfing mechanism is poorly understood in pears. In this research, we discovered that the dwarf hybrid seedlings of pear (Pyrus bretschneideri Rehd.), ‘Red Zaosu,’ exhibited a xylem-deficient dwarf phenotype. The expression level of PbXND1, a suppressor of xylem development, was markedly enhanced in dwarf hybrid seedlings and its overexpression in pear results in a xylem-deficient dwarf phenotype. To further dissect the mechanism of PbXND1, PbTCP4 was isolated as a PbXND1 interaction protein through the pear yeast library. Root transformation experiments showed that PbTCP4 promotes root xylem development. Dual-luciferase assays showed that PbXND1 interactions with PbTCP4 suppressed the function of PbTCP4. PbXND1 expression resulted in a small amount of PbTCP4 sequestration in the cytoplasm and thereby prevented it from activating the gene expression, as assessed by bimolecular fluorescence complementation and co-location analyses. Additionally, PbXND1 affected the DNA-binding ability of PbTCP4, as determined by utilizing an electrophoretic mobility shift assay. These results suggest that PbXND1 regulates the function of PbTCP4 principally by affecting the DNA-binding ability of PbTCP4, whereas the cytoplasmic sequestration of PbTCP4 is only a minor factor. Taken together, this study provides new theoretical support for the extreme dwarfism associated with the absence of xylem caused by PbXND1, and it has significant reference value for the breeding of dwarf varieties and dwarf rootstocks of the pear.

Cold is one of the major limiting factors for citrus production, particularly extreme cold waves. Therefore, it is of great importance to develop cold-tolerant varieties and clarify their cold tolerance mechanisms in citrus breeding. In this study, comparative transcriptomic and physiological analyses were performed to dissect the cold tolerance mechanism of Guijing2501 (GJ2501), a new satsuma mandarin (Citrus unshiu) variety with about 1 °C lower LT50 (the median lethal temperature) relative to Guijing (GJ). The physiological analysis results revealed that GJ2501 is more cold-tolerant with less photoinhibition, PSII photodamage, and MDA accumulation, but higher POD activity than GJ under cold stress. Comparative transcriptomic analysis identified 4200 DEGs between GJ and GJ2501, as well as 4884 and 5580 up-regulated DEGs, and 5288 and 5862 down-regulated DEGs in response to cold stress in GJ and GJ2501, respectively. “Photosynthesis, light harvesting” and “photosystem” were the specific and most significantly enriched GO terms in GJ2501 in response to cold stress. Two CuELIP1 genes (encoding early light-induced proteins) related to the elimination of PSII photodamage and photoinhibition were remarkably up-regulated (by about 1000-fold) by cold stress in GJ2501 as indicated by RT-qPCR verification. Overexpression of CuELIP1 from GJ2501 in transgenic Arabidopsis protected PSII against photoinhibition under cold stress. Taken together, the cold tolerance of GJ2501 may be ascribed to its higher photoprotective capacity under cold stress.