Shoot-Specific Down-Regulation of Protein Farnesyltransferase (α-Subunit) for Yield Protection against Drought in Canola

Abstract

Canola (Brassica napus L.) is one of the most important oilseed crops in the world and its seed yield and quality are significantly affected by drought stress. As an innate and adaptive response to water deficit, land plants avoid potential damage by rapid biosynthesis of the phytohormone abscisic acid (ABA), which triggers stomatal closure to reduce transpirational water loss. The ABA-mediated stomatal response is a dosage-dependent process; thus, one genetic engineering approach for achieving drought avoidance could be to sensitize the guard cell's responsiveness to this hormone. Recent genetic studies have pinpointed protein farnesyltransferase as a key negative regulator controlling ABA sensitivity in the guard cells. We have previously shown that down-regulation of the gene encoding Arabidopsis beta-subunit of farnesyltransferase (ERA1) enhances the plant's sensitivity to ABA and drought tolerance. Although the alpha-subunit of farnesyltransferase (AtFTA) is also implicated in ABA sensing, the effectiveness of using such a gene target for improving drought tolerance in a crop plant has not been validated. Here, we report the identification and characterization of the promoter of Arabidopsis hydroxypyruvate reductase (AtHPR1), which expresses specifically in the shoot and not in non-photosynthetic tissues such as root. The promoter region of AtHPR1 contains the core motif of the well characterized dehydration-responsive cis-acting element and we have confirmed that AtHPR1 expression is inducible by drought stress. Conditional and specific down-regulation of FTA in canola using the AtHPR1 promoter driving an RNAi construct resulted in yield protection against drought stress in the field. Using this molecular strategy, we have made significant progress in engineering drought tolerance in this important crop species.

Diversification and Expression of the PIN, AUX/LAX, and ABCB Families of Putative Auxin Transporters in Populus

“…The PIN genes of Populus present a conserved intron–exon organization which is illustrated in Figure A1 in Appendix. The same structural characteristics are present across PINs from different plant species including Arabidopsis (Mravec et al, 2009; Wang et al, 2009; Shen et al, 2010). The proteins belonging to the PtrPIN family range from 347 to 650 amino acids in length.…”

“…They are also involved in endosperm and embryonic development (Forestan et al, 2010) and in the maintenance of phyllotaxy (Lee et al, 2009). The monocot-specific PINs from rice (OsPIN9, OsPIN10a, and OsPIN10b) are highly expressed in adventitious root primordia and pericycle cells at the stem-base, suggesting that they may have evolved to promote adventitious root development (Wang et al, 2009). …”

Wild Relative and Transgenic Innovation for Enhancing Crop Adaptation to Warmer and Drier Climate

“…Mn-superoxide dismutase (McKersie et al 1996) and antiquitin-like protein (antiquitin catalyses acetaldehyde oxidation) (Rodrigues et al 2006) Enzymes for polyamine synthesis OE Arginine decarboxylase (Capell et al, 2004) and S-adenosylmethionine decarboxylase (Waie & Rajam 2003) TFs involved in drought response OE DREB2A (Sakuma et al 2006b) and ABF3 (Oh et al 2005) TFs involved in cold response OE DREB1A/CBF3 (Kasuga et al 1999) TFs controlling leaf cuticular wax production OE WXP1 (Zhang et al 2005a) TFs involved in regulation of stomatal conductance OE AtMYB61 , SNAC1 (Hu et al 2006) and AtMYB44 (Jung et al 2008) Protein kinases or phosphatase involved in stress signalling OE NPK1 (Shou et al 2004), OsCDPK7 (Saijo et al 2000), and protein phosphatase 2a (Xu et al 2007) Enzymes for ABA synthesis OE AtNCED3 (Iuchi et al 2001) Farnesyltransferases involved in regulation of ABA sensing Repression ERA1 (Wang et al 2005) and FTA (Wang et al 2009) Regulatory proteins not involved in drought response OE Isopentenyltransferase (Rivero et al 2007), 14-3-3 protein GF14 (Yan et al 2004) and homeodomain-START TF (Yu et al 2008) reduction in respiration rate, consequently improving carbon-use efficiency and WUE. Another underexploited area is to use superior alleles from drought-resistant wild or extremophilic species that inhabit extreme drought environments.…”

Genetic Adjustment to Changing Climates: Maize

“…Notable examples are the CAAT box element ZmNF-YB2 (Nelson et al 2007), DREB1A transcription factor (Pellegrineschi et al 2004), MAP kinase NPK1 (Shou et al 2004), drought-responsive elements ABRE and DRE (Narusaka et al 2003), poly (ADPribose) polymerase (Vanderauwera et al, 2007), farsenyl transferase (Wang et al, 2009), late embryogenesis abundant proteins (Xu et al, 1996), NCED2 and LOS5 in ABA biosynthesis, SOS2 in oxygen-radical detoxification (Xiao et al 2008), isopentenyl transferase in cytokinin biosynthesis (Rivero et al 2007), and the mRNA chaperone CspB (Castiglioni et al 2008). A common characteristic of many on these factors is their responsiveness to more than one environmental stress and their impact on the expression of multiple metabolic or structural genes.…”