Point mutations in the stem region and the fourth AAA domain of cytoplasmic dynein heavy chain partially suppress the phenotype of NUDF/LIS1 loss in Aspergillus nidulans

Cytoplasmic dynein performs multiple cellular tasks but its regulation remains unclear. The dynein heavy chain has a N-terminal stem that binds to other subunits and a C-terminal motor unit that contains six AAA (ATPase associated with cellular activities) domains and a microtubule-binding site located between AAA4 and AAA5. In Aspergillus nidulans, NUDF (a LIS1 homolog) functions in the dynein pathway, and two nudF6 partial suppressors were mapped to the nudA dynein heavy chain locus. Here we identified these two mutations. The nudAL1098F mutation resides in the stem region, and nudAR3086C is in the end of AAA4. These mutations partially suppress the phenotype of nudF deletion but do not suppress the phenotype exhibited by mutants of dynein intermediate chain and Arp1. Surprisingly, the stronger DeltanudF suppressor, nudAR3086C, causes an obvious decrease in the basal level of dynein's ATPase activity and an increase in dynein's distribution along microtubules. Thus, suppression of the DeltanudF phenotype may result from mechanisms other than simply the enhancement of dynein's ATPase activity. The fact that a mutation in the end of AAA4 negatively regulates dynein's ATPase activity but partially compensates for NUDF loss indicates the importance of the AAA4 domain in dynein regulation in vivo.

Drought Adaptation in Millets

Millets are major food and feed sources in the developing world especially in the semi-arid tropical regions of Africa and Asia. The most widely cultivated millets are pearl millet [Pennisetum glaucum (L.) R. Br.], finger millet [Eleusine coracana (L.) Gaertn], foxtail millet [Setaria italica (L.) P. Beauvois], Japanese barnyard millet [Echinochloa esculneta (A. Braun) H. Scholz], Indian Barnyard millet [Echinochloa frumetacea Link], kodo millet [Paspalum scrobiculatum L.], little millet [Panicum sumatrense Roth.ex.Roem. & Schult.], proso millet [Panicum miliaceum L.], tef [Eragrostis tef (Zucc.) Trotter] and fonio or acha [Digitaria exilis (Kippist) Stapf and D. iburua Stapf]. Millets are resilient to extreme environmental conditions especially to inadequate moisture and are rich in nutrients. Millets are also considered to be a healthy food, mainly due to the lack of gluten (a substance that causes coeliac disease) in their grain. Despite these agronomic, nutritional and health-related benefits, millets produce very low yield compared to major cereals such as wheat and rice. This extremely low productivity is related to the challenging environment in which they are extensively cultivated and to the little research investment in these crops. Recently, several national and international initiatives have begun to support the improvement of diverse millet types.