Molecular Aspects of Heat Stress Response of Rice Plants

Molecular Aspects of the Heat Stress Response of Rice Plants

by Prof Anil Grover - External examiner- Department of Plant Molecular Biology, University of Delhi South Campus Benito Juarez Road, DhaulaKuan, New Delhi‐110021, India (email:anil.anilgrover@gmail.com)

Rice (Oryzasativa L.) is the most important food crop. The rice transcriptional profile is significantly modulated by heat stress: the enrichment of GO terms protein kinase activity/ protein serine kinase activity, response to heat and reactive oxygen species in up‐regulated genes signifies the role of signal transduction events and reactive oxygen species during early heat stress (Mittal et al. 2012a,b, Sarkar et al. 2014). The proteins associated with chaperones and protein degradation machineries of the cell are stimulated as one of the early steps in minimizing damages to other proteins. Genome‐wide biology of rice Hsp20, Hsp40, Hsp70 and Hsp100 as well as heat shock factors has been unearthed from our studies (Sarkar et al. 2009, Singh et al. 2010, Sarkar et al. 2013a, Sarkar et al.2013b). Rice contains three ClpB/Hsp100 proteins localized to different cellular compartments: cytoplasm/nucleus (OsClpB‐c), mitochondria (OsClpB‐m) and chloroplast (OsClpB‐p) (Mishra and Grover 2015). OsClpB‐c (Os05g44340), OsClpB‐m (Os02g08490) and OsClpB‐p (Os03g31300) proteins are able to complement the thermo‐sensitive phenotype of yeast hsp100 mutant (ΔSchsp104) (Singh and Grover 2010, Singh et al. 2010). Arabidopsis Hot1‐3 is a null mutant for ClpB‐c gene, and is highly thermo‐sensitive both at the seed and seedling levels (Hong and Vierling 2000). We are interested to analyse the strategies of expression of Hsp100 forms which can possibly result into high temperature resistant crops. We have documented that OsHsfA2c (a) has rapid transcript induction under high temperature stress, (b) possesses transactivation activity, (c) forms homo‐oligomeric configuration, (d) regulates expression from OsClpB‐c promoter in heat shock element (HSE)‐dependent manner and (e) interacts with OsClpB‐c and OsHsfB4b proteins (Mittal et al. 2009, Mittal et al. 2011, Singh et al. 2012). We infer that supra‐complexes, involving several OsHsfs, regulate Hsp promoters under high temperature stress in rice.

Sustainable Wheat, Maize and Rice Production

Cereal-based farming systems must join the transition to sustainable agriculture if they are to meet unprecedented demand for maize, rice and wheat. That was one of the key messages to emerge from a crop specialist meeting held by FAO last December. FAO: raw material production must become more sustainable FAO estimates that over the next 35 years farmers will need to increase the annual production of maize, rice and wheat to 3 billion tonnes, or half a billion tonnes more than 2013's record combined harvests. They will need to do that with less water, fossil fuel and agrochemicals, on farmland that has been widely degraded by decades of intensive crop production, and in the face of droughts, new pest and disease threats, and extreme weather events provoked by climate change.

Maize, rice and wheat are fundamental crops 
Experts at the meeting said that the challenge could only be met with eco-friendly agriculture that achieves higher productivity while conserving natural resources, adapting to climate change, and delivering economic benefits to the world's 500 million small-scale family farms. The meeting focused on maize, rice and wheat because those three crops are fundamental to world food security, providing 50% of humanity's dietary energy supply. Cereals are also increasingly vulnerable: climate trends since 1980 have reduced the annual global maize harvest by an estimated 23 million tonnes and the wheat harvest by 33 million tonnes. Green Revolution cereal yield increases, once averaging a spectacular 3% a year, have fallen to around 1% since 2000. In Asia, the degradation of soils and the buildup of toxins in intensive paddy systems have raised concerns that the slowdown in yield growth reflects a deteriorating crop-growing environment.

Input intensive agriculture 
The FAO meeting agreed that agriculture can no longer rely on input-intensive agriculture to increase crop production. Improved varieties of maize, rice and wheat must go hand-in-hand with what FAO calls 'Save and Grow' farming systems that keep soil healthy, integrate crop, tree and animal production, use water far more efficiently, and protect crops with integrated pest management.
EMMY KOELEMAN 12 Jan 2015