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Boron (B) deficiency stress is frequently observed in citrus orchards and causes considerable loss of productivity and fruit quality. Carrizo citrange (Cc) has been reported as a rootstock more tolerant to B deficiency than Trifoliate orange (To). The ‘Newhall’ navel orange (Ns) performed better when grafted onto Cc (Ns/Cc) than when grafted onto To (Ns/To) under long-term B deficiency. The present study confirmed that Ns/Cc had higher boron content, leaf fresh weight, lower leaf chlorosis and stronger photosynthesis ability than Ns/To. Moreover, B-deficiency significantly reduced the chlorophyll and carotenoid content in Ns/To. The content of total soluble sugar and lignin were dramatically increased and the expression levels of photosynthesis-related genes were substantially down-regulated in Ns/To by B-deficient treatment. B-deficiency also strongly induced expression levels of chlorophyll decomposition-related genes, glucose synthesis-related genes and lignin synthesis-related genes, and significantly inhibited the expression of carotenoid synthesis-related genes in Ns/To. Overall, these findings suggested that the influence of To on the scion of Ns was worse than that of Cc due to differently regulating these metabolic pathways under the long term of B-deficiency. The transcriptome analysis provided further information for understanding the mechanism of the different responses of scion-rootstock combinations to B-deficiency stress.

PH5 is a petunia gene that encodes a plasma membrane H(+)-ATPase and determines the vacuolar pH. The citrate content of fruit cell vacuoles influences citrus organoleptic qualities. Although citrus could have PH5-like homologs that are involved in citrate accumulation, the details are still unknown. In this study, extensive data-mining with the PH5 sequence and PCR amplification confirmed that there are at least eight PH5-like genes (CsPH1-8) in the citrus genome. CsPHs have a molecular mass of approximately 100 kDa, and they have high similarity to PhPH5, AtAHA10 or AtAHA2 (from 64.6 to 80.9%). They contain 13-21 exons and 12-20 introns and were evenly distributed into four subgroups of the P3A-subfamily (CsPH1, CsPH2, and CsPH3 in Group I, CsPH4 and CsPH5 in Group II, CsPH6 in Group IV, and CsPH7 and CsPH8 in Group III together with PhPH5). A transcript analysis showed that CsPH1, 3, and 4 were predominantly expressed in mature leaves, whereas CsPH2 and 7 were predominantly expressed in roots, CsPH5 and 6 were predominantly expressed in flowers, and CsPH8 was predominantly expressed in fruit juice sacs (JS). Moreover, the CsPH transcript profiles differed between orange and pummelo, as well as between high-acid and low-acid cultivars. The low-acid orange "Honganliu" exhibits low transcript levels of CsPH3, CsPH4, CsPH5, and CsPH8, whereas the acid-free pummelo (AFP) has only a low transcript level of CsPH8. In addition, ABA injection increased the citrate content significantly, which was accompanied by the obvious induction of CsPH2, 6, 7, and 8 transcript levels. Taken together, we suggest that CsPH8 seems likely to regulate citrate accumulation in the citrus fruit vacuole.

A novel macrocyclic hexanuclear manganese(III) 18-metallacrown-6 compound, [Mn6(H2O)6 (anshz)6] · 10DMF, has been prepared using a trianionic pentadentate ligand N-acetyl-5-nitrosalicylhydrazide (anshz3−) and characterized by X-ray diffraction (DMF = N,N-dimethylformamide). The crystal structure contains a neutral 18-membered metallacrown ring consisting of six Mn(III) and six anshz3− ligands. The 18-membered metallacrown ring is formed by the succession of six structural moieties of the type [Mn(III) N N]. Due to the meridional coordination of the ligand to the Mn3+ ion, the ligand enforces the stereochemistry of the Mn3+ ions as a propeller configuration with alternating Δ/Λ forms. The disc-shaped hexanuclear ring shows at its largest diameter about 7.14 A at entrance, about 9.76 A at the center of the cavity, respectively. Antibacterial screening data showed that the manganese metallacrown has strong antimicrobial activity against Bacillus subtilis.

The asymmetric unit of the title compound, C8H10NO2+·Cl−·H2O, contains two crystallographically independent 2-(methoxy­carbon­yl)anilinium cations related by a pseudo-inversion centre, two chloride ions and two water mol­ecules. A three-dimensional network structure is formed via N—H⋯O, N—H⋯Cl and O—H⋯Cl hydrogen bonds, and π–π stacking inter­actions.

In the title compound, C12H10O3, there are two independent mol­ecules in the asymmetric unit. Both mol­ecules are essentially planar and each features an intra­molecular O—H⋯O hydrogen bond between the hydr­oxy H atom and the carbon­yl O atom. The crystal structure is stabilized by π–π stacking inter­actions.

Sucrose synthase (Sus) (EC 2.4.1.13) is a key enzyme for the sugar accumulation that is critical to form fruit quality. In this study, extensive data-mining and PCR amplification confirmed that there are at least six Sus genes (CitSus1-6) in the citrus genome. Gene structure and phylogeny analysis showed an evolutionary consistency with other plant species. The six Sus genes contain 12-15 exons and 11-14 introns and were evenly distributed into the three plant Sus groups (CitSus1 and CitSus2 in the Sus I group, CitSus3 and CitSus6 in the Sus II group, and CitSus4 and CitSus5 in the Sus III group). Transcripts of these six CitSus genes were subsequently examined. For tissues and organs, CitSus1 and 2 were predominantly expressed in fruit juice sacs (JS) whereas CitSus3 and 4 were predominantly expressed in early leaves (immature leaves), and CitSus5 and 6 were predominantly expressed in fruit JS and in mature leaves. During fruit development, CitSus5 transcript increased significantly and CitSus6 transcript decreased significantly in fruit JS. In the fruit segment membrane (SM), the transcript levels of CitSus2 and 5 were markedly higher and the abundant levels of CitSus3 and 6 gradually decreased. Moreover, transcript levels of CitSus1-4 examined were higher and the CitSus5 transcript level was lower in the fruit SM than in fruit JS, while CitSus6 had a similar transcript level in fruit JS and SM. In addition, transcripts of CitSus1-6 responded differently to dehydration in mature leaves or to mild drought stress in fruit JS and SM. Finally, the possible roles of Sus genes in the regulation of sugar accumulation are discussed; however, further study is required.

In the title crystal structure, C9H12NO2+·Cl−, inter­molecular N—H⋯Cl hydrogen bonds link cations and anions to form one-dimensional ladders propagating in the a-axis direction.

In the title compound, C8H7BrO3, an intra­molecular hydrogen bond exists between the hydroxyl group and the O atom of the carbonyl group. The mol­ecules are stacked along the b axis with weak π–π inter­actions.

The molecule of the title compound, C11H12N2O6, is essentially planar except for the alkyl chain, which has a non-extended conformation.

In the title compound, C10H11NO5, all bond lengths and angles show normal values. Weak inter­molecular O—H⋯O hydrogen bonds form centrosymmetric dimers, which are further linked by π–π inter­actions into ladders extending along the a axis.

In the title compound, C7H13NO4, there are two independent mol­ecules in the asymmetric unit. All bond lengths and angles in the mol­ecules are in normal ranges. The ψ1 and ψ2 torsion angles are 159.9 (4) and −23.4 (5)°, respectively, in the first molecule, and the ψ3 and ψ4 torsion angles 157.7 (4) and −26.7 (5)°, respectively, in the second. Each of the independent mol­ecules has a different comformation. The translationally and screw-related mol­ecules are connected by N—H⋯O hydrogen bonds, forming a two-dimensional network parallel to the ac plane.

The title compound, C10H10N2O6, has two independent mol­ecules in the asymmetric unit. All bond lengths and angles in the mol­ecules are in normal ranges. The crystal packing is stabilized by van der Waals forces and π–π stacking interactions.

In the title compound, C10H10N2O6, the dinitro­benzoate moiety is nearly planar. In the crystal structure, the mol­ecules are stacked along the b axis, without any π–π inter­action.

The structure of the title compound, C8H6N2O6, is essentially planar, except for the meth­yl H atoms. In the crystal structure, the mol­ecules are stacked along the a axis with π–π inter­actions.

In the title mol­ecule, C8H7NO4, the non-H atoms are essentially coplanar. In the crystal structure, short inter­molecular O⋯C (3.21 A) and O⋯N (3.17 A) contacts indicate the presence of π–π inter­actions.

The asymmetric unit of the title compound, C8H7NO5, contains two crystallographically independent mol­ecules. In both mol­ecules, an intramolecular hydrogen bond exists between the hydroxyl group and the O atom of the carbonyl group. The mol­ecules are stacked, with weak π–π interactions, along the a axis.

In the title compound, C13H12O3, there are two independent molecules in the asymmetric unit. Both the molecules are nearly planar and an intramolecular O—H⋯O hydrogen bond is observed between the hydroxy group and the O atom of the carbonyl group. The crystal structure is stabilized by π–π stacking interactions.

Corky split vein caused by boron (B) deficiency in 'Newhall' Navel Orange was studied in the present research. The boron-deficient citrus exhibited a symptom of corky split vein in mature leaves. Morphologic and anatomical surveys at four representative phases of corky split veins showed that the symptom was the result of vascular hypertrophy. Digital gene expression (DGE) analysis was performed based on the Illumina HiSeq™ 2000 platform, which was applied to analyze the gene expression profilings of corky split veins at four morphologic phases. Over 5.3 million clean reads per library were successfully mapped to the reference database and more than 22897 mapped genes per library were simultaneously obtained. Analysis of the differentially expressed genes (DEGs) revealed that the expressions of genes associated with cytokinin signal transduction, cell division, vascular development, lignin biosynthesis and photosynthesis in corky split veins were all affected. The expressions of WOL and ARR12 involved in the cytokinin signal transduction pathway were up-regulated at 1(st) phase of corky split vein development. Furthermore, the expressions of some cell cycle genes, CYCs and CDKB, and vascular development genes, WOX4 and VND7, were up-regulated at the following 2(nd) and 3(rd) phases. These findings indicated that the cytokinin signal transduction pathway may play a role in initiating symptom observed in our study.

The title compound, C8H6N2O7, crystallizes with an intramolecular hydrogen bond between the hydroxyl group and the O atom of the carbonyl group. A weak intermolecular hydrogen bond between the hydroxyl group and a nitro O atom forms planes parallel to the b axis.