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Staying Alive or Going to Die During Terminal Senescence-An Enigma Surrounding Yield Stability.

Jagadish KS, Kavi Kishor PB, Bahuguna RN, von Wirén N, Sreenivasulu N - Front Plant Sci (2015)

Bottom Line: Thus, the consideration of stay-green or senescence phenotypes is still an ongoing debate and has not been comprehensively addressed.While stay-green phenotypes promise to be ideal for developing stress-tolerant lines during pre-anthesis and fertilization to enhance grain number and yield per se, fine-tuning efficient remobilizing behavior during seed filling might optimize grain weight, grain quality and nutrient efficiency.The proposed model provides novel and focused directions for cereal stress breeding programs to ensure better seed-set and efficient grain-filling in cereals under terminal drought and heat stress exposure.

View Article: PubMed Central - PubMed

Affiliation: International Rice Research Institute, Metro Manila , Philippines.

ABSTRACT
Breeding programs with the aim to enhance yield productivity under abiotic stress conditions during the reproductive stage of crops is a top priority in the era of climate change. However, the choice of exploring stay-green or senescence phenotypes, which represent an opposing physiological bearing, are explored in cereal breeding programs for enhanced yield stability to a different extent. Thus, the consideration of stay-green or senescence phenotypes is still an ongoing debate and has not been comprehensively addressed. In this review, we provide arguments for designing a target phenotype to mitigate abiotic stresses during pre- and post-anthesis in cereals with a focus on hormonal balances regulating stay-green phenotype versus remobilization. The two major hypothesis for grain yield improvement are (i) the importance of the stay-green trait to elevate grain number under pre-anthesis and anthesis stress and (ii) fine tuning the regulatory and molecular physiological mechanisms to accelerate nutrient remobilization to optimize grain quality and seed weight under post-anthesis stress. We highlight why a cautious balance in the phenotype design is essential. While stay-green phenotypes promise to be ideal for developing stress-tolerant lines during pre-anthesis and fertilization to enhance grain number and yield per se, fine-tuning efficient remobilizing behavior during seed filling might optimize grain weight, grain quality and nutrient efficiency. The proposed model provides novel and focused directions for cereal stress breeding programs to ensure better seed-set and efficient grain-filling in cereals under terminal drought and heat stress exposure.

No MeSH data available.


Related in: MedlinePlus

Schematic diagram showing integrative effect of stay-green and terminal senescence traits in plants. Extended stay-green trait provides sufficient photosynthate available as transportable sugar (orange arrows) for floral development and higher starch accumulation during grain filling. Conversely, initiation of terminal senescence after seed set provides additional nutrient supply (brown arrows) to the developing grains to improve optimum grain weight and quality. An unknown signaling component (?) from the floral organ (blue arrows) is thought to initiate the senescence process in leaves.
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Figure 1: Schematic diagram showing integrative effect of stay-green and terminal senescence traits in plants. Extended stay-green trait provides sufficient photosynthate available as transportable sugar (orange arrows) for floral development and higher starch accumulation during grain filling. Conversely, initiation of terminal senescence after seed set provides additional nutrient supply (brown arrows) to the developing grains to improve optimum grain weight and quality. An unknown signaling component (?) from the floral organ (blue arrows) is thought to initiate the senescence process in leaves.

Mentions: Several stress factors, in particular drought and heat stress, induced seed yield penalties that were conferred by different phenological alterations in the sink tissue, i.e., during the young microspore stage and subsequently during the anthesis and grain filling stage (Ji et al., 2010). Though crop yield reductions under abiotic stress are mainly a consequence of reduced grain number (Dolferus et al., 2011), the mechanisms of how stay-green phenotypes improve grain number under stress remain poorly understood. A highly flexible and dynamic adjustment due to premature abortion of developing florets under drought or heat stress exposure, can potentially occur throughout the spike development starting from floral meristem differentiation due to sugar starvation (Guo et al., 2015; Li et al., 2015b), which could be averted by reducing ABA level and by elevating brassinosteroids (Ji et al., 2011; Zhu et al., 2015). Under high night temperatures exposure from panicle initiation onwards, a significant floret degeneration was attributed to a competition for assimilates between the growing stem and developing ear (Shi et al., 2013). Moreover, a significant drop in peduncle elongation further increased floret sterility under drought stress mainly due to a shortage of assimilates and competition between stem and ear for the depleted assimilate pool (Jagadish et al., 2010). Two key processes that could determine the viability of reproductive organs and thereby grain numbers are the availability of sufficient amounts of sugars through maintained photosynthesis and efficient sucrose cleavage pathway to channel gradients of hexoses to the developing reproductive tissues (Ji et al., 2010; Dolferus et al., 2011; Suneja et al., 2015). Hence, mechanisms that impact grain numbers through key physiological events including altered male and female gametophyte development, pollen and ovule viability, fertilization events and optimum seed filling are key drivers for maintaining yield under stress (Figure 1).


Staying Alive or Going to Die During Terminal Senescence-An Enigma Surrounding Yield Stability.

Jagadish KS, Kavi Kishor PB, Bahuguna RN, von Wirén N, Sreenivasulu N - Front Plant Sci (2015)

Schematic diagram showing integrative effect of stay-green and terminal senescence traits in plants. Extended stay-green trait provides sufficient photosynthate available as transportable sugar (orange arrows) for floral development and higher starch accumulation during grain filling. Conversely, initiation of terminal senescence after seed set provides additional nutrient supply (brown arrows) to the developing grains to improve optimum grain weight and quality. An unknown signaling component (?) from the floral organ (blue arrows) is thought to initiate the senescence process in leaves.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663250&req=5

Figure 1: Schematic diagram showing integrative effect of stay-green and terminal senescence traits in plants. Extended stay-green trait provides sufficient photosynthate available as transportable sugar (orange arrows) for floral development and higher starch accumulation during grain filling. Conversely, initiation of terminal senescence after seed set provides additional nutrient supply (brown arrows) to the developing grains to improve optimum grain weight and quality. An unknown signaling component (?) from the floral organ (blue arrows) is thought to initiate the senescence process in leaves.
Mentions: Several stress factors, in particular drought and heat stress, induced seed yield penalties that were conferred by different phenological alterations in the sink tissue, i.e., during the young microspore stage and subsequently during the anthesis and grain filling stage (Ji et al., 2010). Though crop yield reductions under abiotic stress are mainly a consequence of reduced grain number (Dolferus et al., 2011), the mechanisms of how stay-green phenotypes improve grain number under stress remain poorly understood. A highly flexible and dynamic adjustment due to premature abortion of developing florets under drought or heat stress exposure, can potentially occur throughout the spike development starting from floral meristem differentiation due to sugar starvation (Guo et al., 2015; Li et al., 2015b), which could be averted by reducing ABA level and by elevating brassinosteroids (Ji et al., 2011; Zhu et al., 2015). Under high night temperatures exposure from panicle initiation onwards, a significant floret degeneration was attributed to a competition for assimilates between the growing stem and developing ear (Shi et al., 2013). Moreover, a significant drop in peduncle elongation further increased floret sterility under drought stress mainly due to a shortage of assimilates and competition between stem and ear for the depleted assimilate pool (Jagadish et al., 2010). Two key processes that could determine the viability of reproductive organs and thereby grain numbers are the availability of sufficient amounts of sugars through maintained photosynthesis and efficient sucrose cleavage pathway to channel gradients of hexoses to the developing reproductive tissues (Ji et al., 2010; Dolferus et al., 2011; Suneja et al., 2015). Hence, mechanisms that impact grain numbers through key physiological events including altered male and female gametophyte development, pollen and ovule viability, fertilization events and optimum seed filling are key drivers for maintaining yield under stress (Figure 1).

Bottom Line: Thus, the consideration of stay-green or senescence phenotypes is still an ongoing debate and has not been comprehensively addressed.While stay-green phenotypes promise to be ideal for developing stress-tolerant lines during pre-anthesis and fertilization to enhance grain number and yield per se, fine-tuning efficient remobilizing behavior during seed filling might optimize grain weight, grain quality and nutrient efficiency.The proposed model provides novel and focused directions for cereal stress breeding programs to ensure better seed-set and efficient grain-filling in cereals under terminal drought and heat stress exposure.

View Article: PubMed Central - PubMed

Affiliation: International Rice Research Institute, Metro Manila , Philippines.

ABSTRACT
Breeding programs with the aim to enhance yield productivity under abiotic stress conditions during the reproductive stage of crops is a top priority in the era of climate change. However, the choice of exploring stay-green or senescence phenotypes, which represent an opposing physiological bearing, are explored in cereal breeding programs for enhanced yield stability to a different extent. Thus, the consideration of stay-green or senescence phenotypes is still an ongoing debate and has not been comprehensively addressed. In this review, we provide arguments for designing a target phenotype to mitigate abiotic stresses during pre- and post-anthesis in cereals with a focus on hormonal balances regulating stay-green phenotype versus remobilization. The two major hypothesis for grain yield improvement are (i) the importance of the stay-green trait to elevate grain number under pre-anthesis and anthesis stress and (ii) fine tuning the regulatory and molecular physiological mechanisms to accelerate nutrient remobilization to optimize grain quality and seed weight under post-anthesis stress. We highlight why a cautious balance in the phenotype design is essential. While stay-green phenotypes promise to be ideal for developing stress-tolerant lines during pre-anthesis and fertilization to enhance grain number and yield per se, fine-tuning efficient remobilizing behavior during seed filling might optimize grain weight, grain quality and nutrient efficiency. The proposed model provides novel and focused directions for cereal stress breeding programs to ensure better seed-set and efficient grain-filling in cereals under terminal drought and heat stress exposure.

No MeSH data available.


Related in: MedlinePlus