Plasma membrane H -ATPase activity and graft success of breadfruit (Artocarpus altilis) onto interspecific rootstocks of marang (A. odoratissimus) and pedalai (A. sericicarpus)

Breadfruit (Artocarpus altilis) is primarily grown as a staple tree crop for food security in the Oceania. Significant wind damage has driven an interest in developing its dwarfing rootstocks. Due to the predominantly vegetative propagation of the species, grafting onto interspecific seedlings is an approach to identifying dwarfing rootstocks. However, grafting of breadfruit onto un-related Artocarpus species has not been investigated. Here we first reported the success of breadfruit grafting onto interspecific rootstocks, marang (A. odoratissimus) and pedalai (A. sericicarpus). To address the low graft survival, we investigated the relationship of plasma membrane (PM) H -ATPase activity to graft success. We provided the first evidences for a positive correlation between PM H -ATPase activity and graft survival. The graft unions of successful grafts had higher PM H -ATPase activity compared to those of failed grafts. Rootstocks with low PM H -ATPase activity in leaf microsomes before grafting had lower graft survival than those with high enzyme activity, with graft success of 10% vs 60% and 0% vs 30% for marang and pedalai rootstocks respectively. There was a positive correlation between graft success and the PM H -ATPase activities measured from the rootstock stem microsomes two months after grafting (marang, r(7) = 0.9203, P= 0.0004; pedalai (r(7) = 0. 8820, P = 0.0017). Removal of scion's own roots decreased the leaf PM H -ATPase activity of grafted plants regardless of the final graft outcome. The recovery of the enzyme activity was only found in the successful grafts. The function of PM H -ATPase in graft union development and graft success improvement is discussed. This article is protected by copyright. All rights reserved

Adequate vitamin D level associated with reduced risk of sporadic colorectal cancer

PurposeThe effect of vitamin D level pertinent to colorectal cancer incidence, progression, or mortality risk is complicated, and study findings are mixed. Therefore, we evaluated whether serum vitamin D [25-hydroxyvitamin D, 25(OH)D] is associated with the incidence of sporadic colorectal cancer (CRC).MethodsThis study is a retrospective analysis of the relationship between serum 25(OH)D level and the risk of CRC. Age, sex, body mass index, history of polyp, disease conditions (i.e., diabetes), medications, and other eight vitamins were used as confounding factors. A total of 389 participants were enrolled in this study, including comprising 83 CRC patients without a family history and 306 healthy controls, between January 2020 and March 2021 at the Department of Colorectal Surgery and Endoscope Center at the Xinhua Hospital, Shanghai Jiao Tong University School of Medicine. Adjusted smoothing spline plots, subgroup analysis, and multivariate logistic regression analysis were conducted to estimate the relative risk between serum 25(OH)D and sporadic CRC risk.ResultsAfter fully adjusting the confounding factors, it was found that circulating 25(OH)D played a protective role in patients with CRC (OR = 0.76 [0.63, 0.92], p = 0.004) and that an adequate vitamin D level was significantly associated with a reduced CRC risk compared to vitamin D deficiency or sufficiency (OR = 0.31 [0.11, 0.9], p = 0.03). According to this study, statins did not affect the potential protective effects of vitamin D (OR = 1.02 [0.97, 1.08], p = 0.44) and may account for the inverse association between serum 25(OH)D and colorectal cancer.ConclusionAn adequate level of serum 25(OH)D was associated with a reduced CRC risk, especially for the elderly. The finding on the absence of protective effect of vitamin D in the statin use subgroup, suggests it may be one of the substantial contributing confounders, and warrants further investigation

Intracellular sucrose communicates metabolic demand to sucrose transporters in developing pea cotyledons

Mechanistic inter-relationships in sinks between sucrose compartmentation/metabolism and phloem unloading/translocation are poorly understood. Developing grain legume seeds provide tractable experimental systems to explore this question. Metabolic demand by cotyledons is communicated to phloem unloading and ultimately import by sucrose withdrawal from the seed apoplasmic space via a turgor-homeostat mechanism. What is unknown is how metabolic demand is communicated to cotyledon sucrose transporters responsible for withdrawing sucrose from the apoplasmic space. This question was explored here using a pea rugosus mutant (rrRbRb) compromised in starch biosynthesis compared with its wild-type counterpart (RRRbRb). Sucrose influx into cotyledons was found to account for 90% of developmental variations in their absolute growth and hence starch biosynthetic rates. Furthermore, rr and RR cotyledons shared identical response surfaces, indicating that control of transporter activity was likely to be similar for both lines. In this context, sucrose influx was correlated positively with expression of a sucrose/H+ symporter (PsSUT1) and negatively with two sucrose facilitators (PsSUF1 and PsSUF4). Sucrose influx exhibited a negative curvilinear relationship with cotyledon concentrations of sucrose and hexoses. In contrast, the impact of intracellular sugars on transporter expression was transporter dependent, with expression of PsSUT1 inhibited, PsSUF1 unaffected, and PsSUF4 enhanced by sugars. Sugar supply to, and sugar concentrations of, RR cotyledons were manipulated using in vitro pod and cotyledon culture. Collectively the results obtained showed that intracellular sucrose was the physiologically active sugar signal that communicated metabolic demand to sucrose influx and this transport function was primarily determined by PsSUT1 regulated at the transcriptional level

Expression of Gibberellin Metabolism Genes and Signalling Components in Dwarf Phenotype of Breadfruit (Artocarpus altilis) Plants Growing on Marang (Artocarpus odoratissimus) Rootstocks

Breadfruit (Artocarpus altilis) is a traditional staple tree crop throughout the tropics. The species is an evergreen tree 15–20 m; there are currently no size-controlling rootstocks within the species. Through interspecific grafting, a dwarf phenotype was identified in breadfruit plants growing on Marang (Artocarpus odoratissimus) rootstocks, which displayed ~60% reduction in plant height with ~80% shorter internodes. To gain insight into the molecular mechanism underlying rootstock-induced dwarfing, we investigated the involvement of gibberellin (GA) in reduction of stem elongation. Expression of GA metabolism genes was analysed in the period from 18 to 24 months after grafting. In comparison to self-graft and non-graft, scion stems on marang rootstocks displayed decrease in expression of a GA biosynthetic gene, AaGA20ox3, and increase in expression of a GA catabolic genes, AaGA2ox1, in the tested 6-month period. Increased accumulation of DELLA proteins (GA-signalling repressors) was found in scion stems growing on marang rootstocks, together with an increased expression of a DELLA gene, AaDELLA1. Exogenous GA treatment was able to restore the stem elongation rate and the internode length of scions growing on marang rootstocks. The possibility that GA deficiency forms a component of the mechanism underlying rootstock-induced breadfruit dwarfing is discussed

Breadfruit (Artocarpus altilis) DELLA genes: gibberellin-regulated stem elongation and response to high salinity and drought

Breadfruit (Artocarpus altilis) is a traditional staple tree crop in the Oceania. Susceptibility to tropical windstorm damage has driven an interest in developing breadfruit with dwarf stature. Gibberellin (GA) is one of the most important determinants of plant height and DELLA proteins are repressors of GA signalling pathway. As a first step toward understanding the molecular mechanism of growth regulation in the species, we isolated two full-length DELLA cDNAs, AaDELLA1 and AaDELLA2 from breadfruit. Sequence analysis indicated the deduced proteins encoded by these AaDELLAs bear all the hallmarks of functional DELLA of other species. Transcripts of AaDELLA1 and AaDELLA2 were detected in all plant organs, but the expression was much lower in flowers and fruits. AaDELLA1 showed predominantly higher expression in roots, but AaDELLA2 displayed higher expression in stems and leaves. Expression of both AaDELLAs was not significantly changed by exogenous GA treatment. Under paclobutrazol treatment, the expression of AaDELLA2 was up-regulated, but the expression of AaDELLA1 was not changed significantly. Treatments of high salinity up-regulated the expression levels of both AaDELLA1 and AaDELLA2. Treatment of drought stress increased the expression of AaDELLA2, but not that of AaDELLA1. The function of AaDELLAs is discussed with particular reference to their role in stem elongation and the opportunities of breadfruit dwarfing

Expression of Gibberellin metabolism genes and signalling components in dwarf phenotype of Breadfruit (Artocarpus altilis) plants growing on Marang (Artocarpus odoratissimus) rootstocks

Breadfruit () is a traditional staple tree crop throughout the tropics. The species is an evergreen tree 15-20 m; there are currently no size-controlling rootstocks within the species. Through interspecific grafting, a dwarf phenotype was identified in breadfruit plants growing on Marang () rootstocks, which displayed ~60% reduction in plant height with ~80% shorter internodes. To gain insight into the molecular mechanism underlying rootstock-induced dwarfing, we investigated the involvement of gibberellin (GA) in reduction of stem elongation. Expression of GA metabolism genes was analysed in the period from 18 to 24 months after grafting. In comparison to self-graft and non-graft, scion stems on marang rootstocks displayed decrease in expression of a GA biosynthetic gene, , and increase in expression of a GA catabolic genes, , in the tested 6-month period. Increased accumulation of DELLA proteins (GA-signalling repressors) was found in scion stems growing on marang rootstocks, together with an increased expression of a DELLA gene, . Exogenous GA treatment was able to restore the stem elongation rate and the internode length of scions growing on marang rootstocks. The possibility that GA deficiency forms a component of the mechanism underlying rootstock-induced breadfruit dwarfing is discussed

Breadfruit (Artocarpus altilis) gibberellin 2-oxidase genes in stem elongation and abiotic stress response

Breadfruit (Artocarpus altilis) is a traditional staple tree crop in the Oceania. Susceptibility to windstorm damage is a primary constraint on breadfruit cultivation. Significant tree loss due to intense tropical windstorm in the past decades has driven a widespread interest in developing breadfruit with dwarf stature. Gibberellin (GA) is one of the most important determinants of plant height. GA 2-oxidase is a key enzyme regulating the flux of GA through deactivating biologically active GAs in plants. As a first step toward understanding the molecular mechanism of growth regulation in the species, we isolated a cohort of four full-length GA2-oxidase cDNAs, AaGA2ox1- AaGA2ox4 from breadfruit. Sequence analysis indicated the deduced proteins encoded by these AaGA2oxs clustered together under the C GA2ox group. Transcripts of AaGA2ox1, AaGA2ox2 and AaGA2ox3 were detected in all plant organs, but exhibited highest level in source leaves and stems. In contrast, transcript of AaGA2ox4 was predominantly expressed in roots and flowers, and displayed very low expression in leaves and stems. AaGA2ox1, AaGA2ox2 and AaGA2ox3, but not AaGA2ox4 were subjected to GA feedback regulation where application of exogenous GA or gibberellin biosynthesis inhibitor, paclobutrazol was shown to manipulate the first internode elongation of breadfruit. Treatments of drought or high salinity increased the expression of AaGA2ox1, AaGA2ox2 and AaGA2ox4. But AaGA2ox3 was down-regulated under salt stress. The function of AaGA2oxs is discussed with particular reference to their role in stem elongation and involvement in abiotic stress response in breadfruit

Total Flavonoid Contents and the Expression of Flavonoid Biosynthetic Genes in Breadfruit (<i>Artocarpus altilis</i>) Scions Growing on Lakoocha (<i>Artocarpus lakoocha</i>) Rootstocks

Breadfruit (Artocarpus altilis) is a traditional fruit tree of 15–30 m height in the tropics. The presence of size-controlling rootstock in the species is not known. A small tropical tree species, lakoocha (Artocarpus lakoocha), was recently identified as a potential vigor-controlling rootstock, conferring over a 65% reduction in breadfruit tree height. To better understand the intriguing scion/rootstock interactions involved in dwarfing, we investigate flavonoid accumulation and its regulation in breadfruit scions in response to different rootstocks. To this end, we isolated a chalcone synthase cDNA, AaCHS, and a full-length bifunctional dihydroflavonol 4-reductase cDNA, AaDFR, from breadfruit scion stems. The expression of both AaCHS and AaDFR genes was examined over the period of 16 to 24 months following grafting. During the development of the dwarf phenotype, breadfruit scion stems on lakoocha rootstocks display significant increases in total flavonoid content, and show upregulated AaCHS expression when compared with those on self-grafts and non-grafts. There is a strong, positive correlation between the transcript levels of AaCHS and total flavonoid content in scion stems. The transcript levels of AaDFR are not significantly different across scions on different rootstocks. This work provides insights into the significance of flavonoid biosynthesis in rootstock-induced breadfruit dwarfing