Study Reveals the Role of Malate Transporters in Rice Grain Yield

Panicle size is a critical factor in grain yield in rice and other grain crops. During rice growth and development, spikelet abortion often occurs at either the top or the basal part of the panicle under unfavorable conditions, causing a reduction in grain yield. Yueqin Heng from the Chinese Academy of Agricultural Sciences studied a rice panicle abortion mutant, panicle apical abortion1-1 (paab1-1), to learn more about spikelet abortion.

The paab1-1 mutant exhibits degeneration of spikelets on the apical portion of panicles during late stage of panicle development. Analysis revealed that the apical spikelets in the paab1-1 mutant undergo programmed cell death. Further analysis revealed that paab1-1 possesses a mutation in the OsALMT7 gene, which encodes an aluminum-activated malate transporter in the plasma membrane, and is expressed in the vascular tissues of developing panicles.

The panicle of the paab1-1 mutant had less malate than wildtypes at the apical portions. Furthermore, injection of malate into the paab1-1 panicle could rescue the spikelet degeneration phenotype. CRISPR-Cas9 knockout of OsALMT7 in rice further confirmed the function of the gene, as the generated CRISPR mutants exhibited the same panicle abortion phenotype as the paab1-1 mutant.

These results suggest that OsALMT7-mediated transport of malate into the apical portion of panicle is required for normal panicle development, highlighting a key role of malate in maintaining the sink size and grain yield in rice.

For more information, read the article in The Plant Cell.