Breadfruit (Artocarpus altilis) gibberellin 20-oxidase genes: sequence variants, stem elongation and abiotic stress response

Abstract

Breadfruit (Artocarpus altilis) is a traditional staple tree crop throughout the tropics. Susceptibility to windstorm damage is the primary constraint on breadfruit cultivation. Significant tree loss due to intense tropical windstorm in the past decades has driven an increasing interest in developing dwarf varieties of breadfruit. As a first step toward understanding the molecular mechanism of growth regulation in the species, we investigated the role of gibberellin and the regulation of GA20-oxidase genes in breadfruit. We provided first evidence that the stem elongation in breadfruit could be manipulated by exogenous gibberellin-related growth regulators. We then cloned six GA20-oxidase cDNAs, AaGA20ox1-AaGA20ox6, in full length from breadfruit. Sequence analysis showed that the predicted proteins of the AaGA20ox1-AaGA20ox3 bear all the hallmarks of functional GA20-oxidase of other species, but predicted AaGA20ox4-AaGA20ox6 as expressed, unprocessed pseudogenes closely related to AaGA20ox2. AaGA20ox1, AaGA20ox3 and AaGA20ox4 were predominantly expressed in green vegetative organs, but displayed different expression pattern in roots and reproductive organs. AaGA20ox2, AaGA20ox5 and AaGA20ox6 were expressed mainly in leaves at low level. AaGA20ox1, AaGA20ox3-AaGA20ox6 were subjected to GA feedback regulation following treatment of exogenous gibberellin and/or gibberellin biosynthesis inhibitors. AaGA20ox1 and AaGA20ox3 were down-regulated under drought and salinity stress, but AaGA20ox2 was upregulated under salt stress. Pseudogenes AaGA20ox4 and AaGA20ox5 were up-regulated under drought or/and salt stress condition. The function of AaGA20oxs is discussed with particular reference to their role in stem elongation and involvement in abiotic stress response in breadfruit.

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

“…Six GA20-oxidase genes, AaGA20ox1-AaGA20ox6, were previously isolated in breadfruits, with three, AaGA20ox1-AaGA20ox3, predicted to encode functional GA20-oxidase and the other three, AaGA20ox4-AaGA20ox6, predicted to be unprocessed pseudogenes [28]. The expression of the three AaGA20oxs, AaGA20ox1-AaGA20ox3, were measured in scion stems, but only two genes, AaGA20ox1 and AaGA20ox3, showed expression in the current experiment condition.…”

“…Each reaction was carried out in duplicate (technical repeat) with non-reverse-transcribed cDNA (RT − ) as negative controls (non-template control). Transcripts of AaGA20oxs and AaGA2oxs were amplified using their gene-specific primers as previously described [28,29]. Gene-specific primers were 5 -GAA AAA GATCAGAAGAAGAAGAATCATCATG-3 and 5 -CCC AAA ACG GCC AGG AGCTCG-3 for AaDELLA2 for AaDELLA1 and 5 -CAT CAG AAG AAGAAT CAT GAA AAG GGA AC-3 and 5 -CAT GTC GGATGA CCT GAC CTT GTA G-3 for AaDELLA2.…”

“…Three predicted functional GA20-oxidases genes were isolated in breadfruit (Artocarpus altilis cv. Cannonball), with two genes, AaGA20ox1 and AaGA20ox3, predominantly expressed in green vegetative organs [28]. A cohort of four GA2-oxidase genes, AaGA2ox1-AaGA2ox4, was also cloned in the same cultivar, with three highly expressed in vegetative organs [29].…”

Combining ability, heritability and genotypic relations of different physiological traits in cacao hybrids

“…Many gene expression studies of the gibberellin biosynthetic pathway have been performed in several fruit tree species and provide insight about aspects of plant growth and development, including those dwarfism or semidwarfism phenotypes related [ 89 – 92 ]. As could be observed in Fig 6 , the relative expression of genes involved in the first two stages of gibberellin biosynthesis showed variation among the parental contrasting genotypes for height.…”

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

“…Breadfruit (A. altilis, cultivar Mason) plants, obtained as rooted cuttings from a nursery at Cap Tribulation, Northern Queensland, were grown under glasshouse condition at 25-28 °C with natural daylight and daily water supply. Plants were grown in pots containing vermiculite and soil mixture as described previously (Zhou and Underhill 2015). For GA 3 or paclobutrazol treatment, both foliage and soil surface were sprayed with 500 mg L −1 GA 3 or paclobutrazol (both from Sigma, St. Lois, USA, dissolved in 0.1% ethanol + 0.1% Triton X-100).…”