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

Abstract

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.

Boosting Crop Yields with Plant Steroids

“…Recently, RNA interference-mediated disruption of the rice SQUALENE SYNTHASE (SQS) gene has been reported to reduce the stomatal conductance and to improve drought tolerance at both the vegetative and reproductive stages (Manavalan et al, 2012). Given that SQS catalyzes the first reaction of the isoprenoid metabolic pathway committed to sterol synthesis, these results suggest that decreased sterol and BR content might enhance stress tolerance and confirm the potential of manipulating plant steroid content to increase crop yield under stress conditions.…”

Plant hormones in salt stress tolerance

“…Although the positive role of BRs in promoting tolerance to a wide range of abiotic stresses have been reported, the molecular mechanisms explaining how BRs control stress responses and regulate stress-responsive gene expression in plants are largely unknown. Recent molecular studies have demonstrated the positive role of BR application or endogenous BR contents in salt and drought stress (Krishna 2003;Koh et al 2007;Manavalan et al 2012). Enhancing BR signaling activity in Arabidopsis led to increase salt stress tolerances, but BR defective mutants showed hyper salt stress responses (Krishna 2003).…”

“…Consistently, BRs treatment could remove the salinity-induced inhibition of seed germination and seedling growth in rice. Moreover, increasing endogenous BR levels by gene silencing-mediated disruption SQS (Squalene synthase) gene involving in critical function for BRs biosynthesis led to increase in salt stress tolerance (Manavalan et al 2012). Together, these imply the positive roles of BRs in plant salt and drought stress tolerances.…”

Tackling Drought Stress: RECEPTOR-LIKE KINASES Present New Approaches

“…Components of the second group have functions in membrane protection, including production of osmoprotectants and antioxidants as well as reactive oxygen species scavengers. All of these processes have been major targets of genetic engineering approaches to produce plants that have enhanced stress tolerance (Valliyodan and Nguyen, 2006;Trujillo et al, 2008;Goel et al, 2010;Quan et al, 2010;Manavalan et al, 2012).…”