RNAi-mediated disruption of squalene synthase improves drought tolerance and yield in rice

About one-third of the world’s rice area is in rain-fed lowlands and most are prone to water shortage. The identification of genes imparting tolerance to drought in the model cereal plant, rice, is an attractive strategy to engineer improved drought tolerance not only rice but other cereals as well. It is demonstrated that RNAi-mediated disruption of a rice farnesyltransferase/squalene synthase (SQS) by maize squalene synthase improves drought tolerance at both the vegetative and reproductive stages. Twenty-day-old seedlings of wild type (Nipponbare) and seven independent events of transgenic RNAi lines showed no difference in morphology. When subjected to water stress for a period of 32 d under growth chamber conditions, transgenic positives showed delayed wilting, conserved more soil water, and improved recovery. When five independent events along with wild-type plants were subjected to drought at the reproductive stage under greenhouse conditions, the transgenic plants lost water more slowly compared with the wild type, through reduced stomatal conductance and the retention of high leaf relative water content (RWC). After 28 d of slow progressive soil drying, transgenic plants recovered better and flowered earlier than wild-type plants. The yield of water-stressed transgenic positive plants ranged from 14–39% higher than wild-type plants. When grown in plates with Yoshida’s nutrient solution with 1.2% agar, transgenic positives from three independent events showed increased root length and an enhanced number of lateral roots. The RNAi-mediated inactivation produced reduced stomatal conductance and subsequent drought tolerance

Identification of Novel QTL Governing Root Architectural Traits in an Interspecific Soybean Population

Cultivated soybean (Glycine max L.) cv. Dunbar (PI 552538) and wild G. soja (PI 326582A) exhibited significant differences in root architecture and root-related traits. In this study, phenotypic variability for root traits among 251 BC2F5 backcross inbred lines (BILs) developed from the cross Dunbar/PI 326582A were identified. The root systems of the parents and BILs were evaluated in controlled environmental conditions using a cone system at seedling stage. The G. max parent Dunbar contributed phenotypically favorable alleles at a major quantitative trait locus on chromosome 8 (Satt315-I locus) that governed root traits (tap root length and lateral root number) and shoot length. This QTL accounted for \u3e10% of the phenotypic variation of both tap root and shoot length. This QTL region was found to control various shoot- and root-related traits across soybean genetic backgrounds. Within the confidence interval of this region, eleven transcription factors (TFs) were identified. Based on RNA sequencing and Affymetrix expression data, key TFs including MYB, AP2-EREBP and bZIP TFs were identified in this QTL interval with high expression in roots and nodules. The backcross inbred lines with different parental allelic combination showed different expression pattern for six transcription factors selected based on their expression pattern in root tissues. It appears that the marker interval Satt315–I locus on chromosome 8 contain an essential QTL contributing to early root and shoot growth in soybean

Epistatic QTLs identified for root dry weight with LOD value < 5.0 in Dunbar/PI 326582A population.

<p>AE: Additive effect; PVE: Phenotypic variation explained in per cent; AA: Additive x Additive interaction</p><p>⁺Positive value indicate that the Dunbar allele increase the phenotypic value.</p><p>Epistatic QTLs identified for root dry weight with LOD value < 5.0 in Dunbar/PI 326582A population.</p

Candidate genes identified on QTL region on chromosome 8 and their expression pattern in 12 soybean tissues derived from Affymetrix gene chip data in Genevestigator software.

<p>Candidate genes identified on QTL region on chromosome 8 and their expression pattern in 12 soybean tissues derived from Affymetrix gene chip data in Genevestigator software.</p

Root architecture contrasts between the two parents at: a) 12 days; b) 21 days; and c) 35 days after sowing.

<p>Root architecture contrasts between the two parents at: a) 12 days; b) 21 days; and c) 35 days after sowing.</p

Distribution of means of 251 BILs for root and shoot traits.

<p>Parental values are indicated by arrows.</p

Co-location of other plant and seed morphology traits in the identified candidate QTL region on chromosome 8.

<p>Co-location of other plant and seed morphology traits in the identified candidate QTL region on chromosome 8.</p