ABSTRACT
The fresh water unicellular alga Haematococcus pluvialis is a promising natural source of astaxanthin. The present study investigated the transcriptional expression of carotenoid genes for astaxanthin accumulation in H. pluvialis using real-time fluorescence quantitative PCR (qRT-PCR). With treatments of 20 and 40 mg/L of gibberllin A3 (GA3), five genes ipi-1, ipi-2, psy, pds and bkt2 were up-regulated with different expression profiles. GA20 (20 mg/L of GA3) treatment had a greater effect on transcriptional expression of bkt2 than on ipi-1 ipi-2, psy and pds (>4-fold up-regulation). However, GA40 (40 mg/L of GA3) induced more transcriptional expression of ipi-2, psy and bkt2 than both ipi-1 and pds. The expression of lyc, crtR-B and crtO for astaxanthin biosynthesis was not affected by GA3 in H. piuvialis. In the presence of GA3, astaxanthin biosynthesis genes of ipi-1, pds and bkt2 were up-regulated at transcriptional level, psy at post-transcriptional level, whereas ipi-2 was up-regulated at both levels. The study could potentially lead to a scale application of exogenous GA3 in astaxanthin production with H. pluvialis just like GAs perform in increasing crops production and it would provide new insight about the multifunctional roles of carotenogenesis in response to GA3.
Subject(s)
Carotenoids/genetics , Dose-Response Relationship, Drug , Fresh Water , Gene Expression Regulation, Plant/drug effects , Gibberellins/pharmacology , Plant Growth Regulators/pharmacology , Transcription, Genetic/drug effects , Volvocida/drug effects , Volvocida/genetics , Volvocida/metabolism , Xanthophylls/metabolismABSTRACT
Treatment of a salt tolerant variety of mustard (Brassica juncea cv RH30), with 0.2M NaCl for 96 hr was found to induce synthesis of three new polypeptides and accumulation of proline. A cDNA library from mRNAs derived from salt stressed plants was constructed in the expression vector lambda gt11. Screening by differential hybridization and by salt stress specific antibodies gave two clones msc1 and msc2 (mustard salt clone) respectively. msc1 hybridized to transcripts from salt stressed mustard seedlings only after 48 hr of 0.2M NaCl stress as also to transcripts from drought stress induced by 10% PEG for 24 hr. msc 1 cross hybridized with msc2 clone. The results show the common mechanism of stress response as elicited in other plants.