Expression of six malate-related genes in pulp during the fruit development of two loquat (<i>Eriobotrya japonica</i>) cultivars differing in fruit acidity

Abstract

Partial cDNAs encoding phosphoenolpyruvate carboxylase (PEPC), NADP-malic enzyme (NADP-ME), cytosolic NAD-malate dehydrogenase (cyNAD-MDH), mitochondrial NAD-malate dehydrogenase (mNAD-MDH), tonoplast adenosinetriphosphatase subunit A (V-ATPase A) and tonoplast pyrophosphatase (V-PPiase) were isolated from loquat (Eriobotrya japonica) pulp. Thereafter, northern analysis was performed to investigate their expression patterns in pulp during the fruit development of low-acid ‘Changhong 3’ and high-acid ‘Jiefangzhong’ cultivars. All gene expressions were developmentally regulated in two cultivars. NADP-ME, mNAD-MDH, V-ATPase A and V-PPiase displayed basically similar expression patterns in both cultivars, but the expression level of NADP-ME in ‘Jiefangzhong’ was higher, while the expression levels of mNAD-MDH, V-ATPase A and V-PPiase in ‘Changhong 3’ was higher. The expression patterns of PEPC and cyNAD-MDH differed between two cultivars. The activities of PEPC, NADP-ME, cyNAD-MDH, mNAD-MDH, V-ATPase and V-PPiase during the fruit development might be regulated at the gene expression and/or the post-transcriptional level. The possible links between gene expression and malate concentration were also discussed.

Key words: Eriobotrya japonica (loquat) fruit, NAD-malate dehydrogenase, NADP-malic enzyme, phosphoenolpyruvate carboxylase, tonoplast adenosinetriphosphatase, tonoplast pyrophosphatase.