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Developmental changes in the composition of leaf cuticular wax of banana influenced by wax biosynthesis gene expression: a case study in Musa acuminata and Musa balbisiana

Sampangi-Ramaiah, Megha Hastantram, Ravishankar, Kundapura Venkataramana, Shivashankar, Kodthalu Seetharamaiah, Roy, Tapas Kumar, Rekha, Ajitha, Hunashikatti, Laxman R.
Acta physiologiae plantarum 2019 v.41 no.8 pp. 141
Musa acuminata subsp. burmannica, Musa balbisiana, bananas, biosynthesis, case studies, developmental stages, drought tolerance, epicuticular wax, fatty acids, gas chromatography-mass spectrometry, gene expression, genes, genotype, leaves, quantitative polymerase chain reaction, water holding capacity
The composition of the cuticular wax varies from species to species as well as the developmental stage of the organ. In the present study, the variation in the pattern of accumulation of C₂₈ and > C₂₈ chain length of the cuticular wax compounds in the two contrasting Musa species for wax content has been examined—Musa balbisiana ‘Bee heekela’ (BB genome) (with high wax content) and Musa acuminata ssp. Burmannicoides Colla—‘Calcutta-4’ (AA genome) (with low wax content). These two species are the progenitors for the modern cultivated banana. Using GC–MS analysis, 40 different cuticular wax compounds from five different leaf developmental stages in these two musa species were identified. Around tenfold higher accumulation of C₂₈ length compounds was found in ‘Calcutta-4’ as compared to that of ‘Bee hee kela’. In case of ‘Bee hee kela’, > C₂₈ length compounds were in large proportion compared to C₂₈ length wax compounds. The qPCR analysis was carried out for the gene CUT1/CER6/KCS6 which are involved in the fatty acid elongation step of cuticular wax biosynthesis. A higher expression in the 2nd (young), 4th and 6th (old) fully expanded leaves of high wax genotype ‘Bee hee kela’ with 1.57083, 9.71512, and 1.44963 fold change, whereas a lower expression of 0.9151, 4.8785, and 1.2321 fold change in low wax genotype ‘Calcutta-4’, respectively, was observed. A negative relationship between the gene expression and C₂₈ wax compounds’ accumulation was observed, indicating the importance of the expression of CUT1/CER6/KCS6 gene for elongation of C₂₈ to > C₂₈ cuticular wax compounds. The current study suggest that CUT1/CER6/KCS6 from ‘Bee heekela’ would be a good contributor for higher cuticular wax with higher > C₂₈ compounds, thus, finally, contributing for higher leaf water retention capacity their by conferring drought tolerance helping in the future banana improvement programs.