Mechanisms of Progressive Water Deficit Tolerance and Growth Recovery of Chinese Maize Foundation Genotypes Huangzao 4 and Chang 7-2, Which are Proposed on the Basis of Comparison of Physiological and Transcriptomic Responses

Abstract

The maize inbred lines Huangzao 4 (HZ4) and Chang 7-2 (C7-2) are the foundation genotypes key to maize cross-breeding in China. C7-2 is derived from HZ-4. In this study, changes in phenotype, physiology and gene expression of three-leaf-old seedlings of HZ4 and C7-2 under the conditions of progressive water deficit (WD) and re-watering (RW) were compared to gain knowledge for breeding new maize foundation genotypes with higher drought tolerance. Progressive WD was produced by adding polyethylene glycol (PEG 6000) at 24 h intervals (24, 48 and 72 h) in Hoagland's nutrient solution, resulting in water potentials of -0.15, -0.3 and -0.5 MPa. The seedlings treated for 24 h at -0.5 [corrected] MPa were subjected to RW in the solution without complementation with PEG. The results showed that C7-2 seedlings are more tolerant to progressive WD than HZ4 seedlings in part because the former have a larger stomatal resistance, a relatively stronger leaf water-holding capacity, and a timely and stable increase in activities of antioxidant enzymes (superoxide dismutase and peroxidase) especially in roots upon WD. Oligonucleotide probe array-based analysis uncovered a number of WD- and RW-regulated genes in both inbred lines, and clearly indicated that fine transcriptional coordination between maize leaves and roots is one of the factors constituting higher WD tolerance and a greater ability for growth recovery from WD. On the basis of the resulting data and co-regulation of responsive genes in tissues, we propose a model for the whole maize plant tolerance to growth and recovery from WD.

Identification of candidate genes for drought tolerance by whole-genome resequencing in maize

“…For transcriptome analysis, the seeds of maize inbred AC7643 were surface-sterilized and grew in the same nutrient solution and environment condition as reported [80]. At the three-leaf-stage, 20% PEG were subjected for 24 h and the roots of inbred AC7643 under well-watered and drought-stressed conditions were sampled for RNA extraction separately using TRIzol® reagent (Invitrogen, USA), RNA sequencing were performed at BGI-Shenzhen (Shenzhen, China) using Illumina deep sequencing according to the manufacturer’s instructions.…”

Application of proline to root medium is more effective for amelioration of photosynthetic damages as compared to foliar spraying or seed soaking in maize seedlings under short-term drought

“…For rooting medium treatment, 0, 1, 10, and 20 mM PRO was added to Hoagland nutrient solution and PRO pretreatments were performed for 2 days. After that, 23-day-old plants were exposed to gradual drought stress induced by dissolving polyethylene glycol (PEG 6000 ) in the nutrient solution in three equal increasing doses with an interval of 8 h until the final concentration of 20% to develop a water potential of -0.5 MPa, similar to Li et al (2009). After that, the seedlings were subjected to drought stress for 8 h and thus they were cultured in different hydroponic systems designed as follows.…”

Antioxidant and carbohydrate changes of two pomegranate cultivars under deficit irrigation stress

“…These defense mechanisms include antioxidant systems (Li et al, 2009;Aghaleh et al, 2010) and osmotic adjustment (by increasing of compatible metabolites) (Hongbo et al, 2006). Plant antioxidants contain enzymatic and non-enzymatic systems.…”