Nucleotides, micro- and macro-nutrients, limonoids, flavonoids, and hydroxycinnamates composition in the phloem sap of sweet orange

Abstract

Currently, the global citrus production is declining due to the spread of Huanglongbing (HLB). HLB, otherwise known as citrus greening, is caused by Candidatus Liberibacter asiaticus (CLas) and is transmitted by the Asian citrus psyllids (ACP), Diaphorina citri Kuwayama. ACP transmits CLas bacterium while feeding on the citrus phloem sap. Multiplication of CLas in the phloem of citrus indicates that the sap contains all the essential nutrients needed for CLas. In this study, we investigated the micro-and macro-nutrients, nucleotides, and others secondary metabolites of phloem sap from pineapple sweet orange. The micro-and macro-nutrients were analyzed using inductively coupled plasma-mass spectroscopy (ICP-MS) and inductively coupled plasma-optical emission spectroscopy (ICP-OES). Nucleotides and other secondary metabolites analysis was accomplished by reversed phase HPLC coupled with UV, fluorescence detection, or negative mode electrospray ionization mass spectrometry (ESI-MS). Calcium (89 mM) was the highest element followed by potassium (38.8 mM) and phosphorous (24 mM). Magnesium and sulfur were also abundant and their concentrations were 15 and 9 mM, respectively. The rest of the elements were found in low amounts (< 2mM). The concentrations of ATP, ADP, and AMP were 16, 31, and 3 m mole/Kg fwt, respectively. GTP, GMP. NAD, FMN, FAD, and riboflavin were found at concentrations below (3 m mole/Kg fwt). The phloem was rich in nomilin 124 mM and limonin 176 m mole/Kg fwt. Hesperidin, vicenin-2, sinensetin, and nobiletin were the most predominant flavonoids. In addition, several hydroxycinnamates were detected. The results of this study will increase our knowledge about the nature and the chemical composition of citrus phloem sap.

Behavioral Plasticity in Probing by Diaphorina citri (Hemiptera, Liviidae): Ingestion from Phloem Versus Xylem is Influenced by Leaf Age and Surface

“…Second, these difference may be a strategic change in the psyllid wherein phloem ingestion is elevated on flush, in preparation for reproduction, while greatly reduced on mature leaves where the psyllid only needs to survive until flush is present. Third, the reduced nutritive content of phloem fluids in mature leaves could be a form of host plant resistance, as was demonstrated in a resistant sugarcane cultivar (Akbar et al 2014 ; Hijaz et al 2016 ).…”

“…Of these factors, nutrition may be especially important. The general conclusion of several recent papers (Hijaz et al 2016 ; Killiny 2017 ; Setamou et al 2016 ; Valim and Killiny 2017 ) is that the nutritional composition of phloem changes depending on the species, cultivar, and the age of the plant tissues. Based on this literature, we can conclude that there were nutritional differences between immature and mature leaves in our experiment, and similar experiments by others (George et al 2017 ; Luo et al 2015 ), as well as nutritional differences due to host species and cultivar used in each study.…”

Metabolomic analyses of the haemolymph of the Asian citrus psyllid Diaphorina citri, the vector of huanglongbing

“…Phosphoric acid is found at high level in the haemolymph. Phosphoric acid is reported in the haemolymph of honey bee (Aliferis et al ., ) and the phloem sap of many plants, including citrus (Dinant et al ., ; Hijaz et al ., ). Besides phosphoric acid, many organic acids are detected in the haemolymph.…”

“…In addition, many sugar nucleotides such as UDP‐G and GDP‐G are detected in plant tissues (Nieman & Clark, ). ATP, ADP, AMP, GTP and GMP, NAD, NADP, riboflavin 5′‐phosphate sodium salt hydrate (FMN), FAD and riboflavin are reported recently as being detected in tissue of citrus phloem sap (Hijaz et al ., ).…”

Zinc is an inhibitor of the LdtR transcriptional activator

“…Recently, in a characterization of the composition of the phloem sap of Citrus sinensis (var. pineapple sweet orange), it was found that the phloem sap is rich in flavonoids, hydroxycinnamates, nucleotides, macro- and micro-nutrients [ 16 ]. The most abundant macro-nutrients were calcium and magnesium, whereas the most abundant micro-nutrients were zinc and manganese [ 16 ].…”