Green-fruited Solanum habrochaites lacks fruit-specific carotenogenesis due to metabolic and structural blocks

Himabindu Vasuki Kilambi, Kalyani Manda, Avanish Rai, Chaitanya Charakana, Jayram Bagri, Rameshwar Sharma, Yellamaraju Sreelakshmi*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Members of the tomato clade exhibit a wide diversity in fruit color, but the mechanisms governing inter-species diversity of coloration are largely unknown. The carotenoid profiles, carotenogenic gene expression and proteome profiles of green-fruited Solanum habrochaites (SH), orange-fruited S. galapagense, and red-fruited S. pimpinellifolium were compared with cultivated tomato [S. lycopersicum cv. Ailsa Craig (SL)] to decipher the molecular basis of coloration diversity. Green-fruited SH, though it showed normal expression of chromoplast-specific phytoene synthase1 and lycopene β-cyclase genes akin to orange/red-fruited species, failed to accumulate lycopene and β-carotene. The SH phytoene synthase1 cDNA encoded an enzymatically active protein, whereas the lycopene β-cyclase cDNA was barely active. Consistent with its green-fruited nature, SH's fruits retained chloroplast structure and PSII activity, and had impaired chlorophyll degradation with high pheophorbide a levels. Comparison of the fruit proteomes with SL revealed retention of the proteome complement related to photosynthesis in SH. Targeted peptide monitoring revealed a low abundance of key carotenogenic and sequestration proteins in SH compared with tomato. The green-fruitedness of SH appears to stem from blocks at several critical steps regulating fruit-specific carotenogenesis namely the absence of chloroplast to chromoplast transformation, block in carotenoid biosynthesis, and a dearth of carotenoid sequestering proteins.

Original languageEnglish
Pages (from-to)4803-4819
Number of pages17
JournalJournal of Experimental Botany
Volume68
Issue number17
DOIs
StatePublished - 1 Aug 2017
Externally publishedYes

Keywords

  • Carotenoid biosynthesis
  • carotenoid sequestration
  • fruit color
  • gene expression
  • proteome analysis
  • tomato clade

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