Sugarcane is a unique crop with the ability to accumulate high levels of sugar and is a commercially viable source of biomass for bioelectricity and second-generation bioethanol. Water deficit is the single largest abiotic stress affecting sugarcane productivity and the development of water use efficient and drought tolerant cultivars is an imperative for all major sugarcane producing countries. This review summarizes the physiological and molecular studies on water deficit stress in sugarcane, with the aim to help formulate more effective research strategies for advancing our knowledge on genes and mechanisms underpinning plant response to water stress. We also overview transgenic studies in sugarcane, with an emphasis on the potential strategies to develop superior sugarcane varieties that improve crop productivity in drought-prone environments.
The molecular basis of anhydrobiosis, the state of suspended animation entered by
some species during extreme desiccation, is still poorly understood despite a
number of transcriptome and proteome studies. We therefore conducted functional
screening by RNA interference (RNAi) for genes involved in anhydrobiosis in the
holo-anhydrobiotic nematode Panagrolaimus superbus. A new
method of survival analysis, based on staining, and proof-of-principle RNAi
experiments confirmed a role for genes involved in oxidative stress tolerance,
while a novel medium-scale RNAi workflow identified a further 40
anhydrobiosis-associated genes, including several involved in proteostasis, DNA
repair and signal transduction pathways. This suggests that multiple genes
contribute to anhydrobiosis in P. superbus.
The successful development of genetically engineered monocots using
Agrobacterium-mediated transformation has created an
increasing demand for compatible vectors. We have developed a new expression
vector, pGVG, for efficient transformation and expression of different
constructs for gene overexpression and silencing in sugarcane. The pCAMBIA2300
binary vector was modified by adding Gateway recombination sites for fast gene
transfer between vectors and the maize polyubiquitin promoter Ubi-1
(ZmUbi1), which is known to drive high gene expression
levels in monocots. Transformation efficiency using the pGVG vector reached up
to 14 transgenic events per gram of transformed callus. Transgenic plants
expressing the β-glucuronidase (GUS) reporter gene from pGVG
showed high levels of GUS activity. qRT-PCR evaluations demonstrated success for
both overexpression and hairpin-based silencing cassettes. Therefore, pGVG is
suitable for plant transformation and subsequent applications for
high-throughput production of stable transgenic sugarcane. The use of an
expression cassette based on the ZmUbi1 promoter opens the
possibility of using pGVG in other monocot species.
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